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window.onload = function () {pageLoad();setSynopsis("mini_Data-Text.html");};
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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Data-Text.html">Source</a></li><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">text-0.11.1.13: An efficient packed Unicode text type.</p></div><div id="content"><div id="module-header"><table class="info"><tr><th>Portability</th><td>GHC</td></tr><tr><th>Stability</th><td>experimental</td></tr><tr><th>Maintainer</th><td>bos@serpentine.com, rtomharper@googlemail.com,
duncan@haskell.org</td></tr><tr><th>Safe Haskell</th><td>Safe-Infered</td></tr></table><p class="caption">Data.Text</p></div><div id="table-of-contents"><p class="caption">Contents</p><ul><li><a href="#g:1">Strict vs lazy types
</a></li><li><a href="#g:2">Acceptable data
</a></li><li><a href="#g:3">Fusion
</a></li><li><a href="#g:4">Types
</a></li><li><a href="#g:5">Creation and elimination
</a></li><li><a href="#g:6">Basic interface
</a></li><li><a href="#g:7">Transformations
</a><ul><li><a href="#g:8">Case conversion
</a></li><li><a href="#g:9">Justification
</a></li></ul></li><li><a href="#g:10">Folds
</a><ul><li><a href="#g:11">Special folds
</a></li></ul></li><li><a href="#g:12">Construction
</a><ul><li><a href="#g:13">Scans
</a></li><li><a href="#g:14">Accumulating maps
</a></li><li><a href="#g:15">Generation and unfolding
</a></li></ul></li><li><a href="#g:16">Substrings
</a><ul><li><a href="#g:17">Breaking strings
</a></li><li><a href="#g:18">Breaking into many substrings
</a></li><li><a href="#g:19">Breaking into lines and words
</a></li></ul></li><li><a href="#g:20">Predicates
</a><ul><li><a href="#g:21">View patterns
</a></li></ul></li><li><a href="#g:22">Searching
</a></li><li><a href="#g:23">Indexing
</a></li><li><a href="#g:24">Zipping and unzipping
</a></li></ul></div><div id="description"><p class="caption">Description</p><div class="doc"><p>A time and space-efficient implementation of Unicode text.
Suitable for performance critical use, both in terms of large data
quantities and high speed.
</p><p><em>Note</em>: Read below the synopsis for important notes on the use of
this module.
</p><p>This module is intended to be imported <code>qualified</code>, to avoid name
clashes with <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Prelude.html">Prelude</a> functions, e.g.
</p><pre> import qualified Data.Text as T
</pre><p>To use an extended and very rich family of functions for working
with Unicode text (including normalization, regular expressions,
non-standard encodings, text breaking, and locales), see the
<code>text-icu</code> package: <a href="http://hackage.haskell.org/package/text-icu">http://hackage.haskell.org/package/text-icu</a>
</p></div></div><div id="synopsis"><p id="control.syn" class="caption expander" onclick="toggleSection('syn')">Synopsis</p><ul id="section.syn" class="hide" onclick="toggleSection('syn')"><li class="src short"><span class="keyword">data</span> <a href="#t:Text">Text</a> </li><li class="src short"><a href="#v:pack">pack</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-String.html#t:String">String</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:unpack">unpack</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-String.html#t:String">String</a></li><li class="src short"><a href="#v:singleton">singleton</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:empty">empty</a> :: <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:cons">cons</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:snoc">snoc</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:append">append</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:uncons">uncons</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:head">head</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:last">last</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:tail">tail</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:init">init</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:null">null</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a></li><li class="src short"><a href="#v:length">length</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a></li><li class="src short"><a href="#v:compareLength">compareLength</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Ord.html#t:Ordering">Ordering</a></li><li class="src short"><a href="#v:map">map</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:intercalate">intercalate</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>] -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:intersperse">intersperse</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:transpose">transpose</a> :: [<a href="Data-Text.html#t:Text">Text</a>] -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:reverse">reverse</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:replace">replace</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:toCaseFold">toCaseFold</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:toLower">toLower</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:toUpper">toUpper</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:justifyLeft">justifyLeft</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:justifyRight">justifyRight</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:center">center</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:foldl">foldl</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> a) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> a</li><li class="src short"><a href="#v:foldl-39-">foldl'</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> a) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> a</li><li class="src short"><a href="#v:foldl1">foldl1</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:foldl1-39-">foldl1'</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:foldr">foldr</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> a -> a) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> a</li><li class="src short"><a href="#v:foldr1">foldr1</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:concat">concat</a> :: [<a href="Data-Text.html#t:Text">Text</a>] -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:concatMap">concatMap</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:any">any</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a></li><li class="src short"><a href="#v:all">all</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a></li><li class="src short"><a href="#v:maximum">maximum</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:minimum">minimum</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:scanl">scanl</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:scanl1">scanl1</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:scanr">scanr</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:scanr1">scanr1</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:mapAccumL">mapAccumL</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> (a, <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>)) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> (a, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:mapAccumR">mapAccumR</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> (a, <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>)) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> (a, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:replicate">replicate</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:unfoldr">unfoldr</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>, a)) -> a -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:unfoldrN">unfoldrN</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>, a)) -> a -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:take">take</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:drop">drop</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:takeWhile">takeWhile</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:dropWhile">dropWhile</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:dropWhileEnd">dropWhileEnd</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:dropAround">dropAround</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:strip">strip</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:stripStart">stripStart</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:stripEnd">stripEnd</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:splitAt">splitAt</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:breakOn">breakOn</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:breakOnEnd">breakOnEnd</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:break">break</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:span">span</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:group">group</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:groupBy">groupBy</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:inits">inits</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:tails">tails</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:splitOn">splitOn</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:split">split</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:chunksOf">chunksOf</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:lines">lines</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:words">words</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]</li><li class="src short"><a href="#v:unlines">unlines</a> :: [<a href="Data-Text.html#t:Text">Text</a>] -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:unwords">unwords</a> :: [<a href="Data-Text.html#t:Text">Text</a>] -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:isPrefixOf">isPrefixOf</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a></li><li class="src short"><a href="#v:isSuffixOf">isSuffixOf</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a></li><li class="src short"><a href="#v:isInfixOf">isInfixOf</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a></li><li class="src short"><a href="#v:stripPrefix">stripPrefix</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:stripSuffix">stripSuffix</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:commonPrefixes">commonPrefixes</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:filter">filter</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li><li class="src short"><a href="#v:breakOnAll">breakOnAll</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> [(<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)]</li><li class="src short"><a href="#v:find">find</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:partition">partition</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)</li><li class="src short"><a href="#v:index">index</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:findIndex">findIndex</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a></li><li class="src short"><a href="#v:count">count</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a></li><li class="src short"><a href="#v:zip">zip</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> [(<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>, <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>)]</li><li class="src short"><a href="#v:zipWith">zipWith</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a></li></ul></div><div id="interface"><h1 id="g:1">Strict vs lazy types
</h1><div class="doc"><p>This package provides both strict and lazy <code><a href="Data-Text.html#t:Text">Text</a></code> types. The
strict type is provided by the <code><a href="Data.html#t:Text">Text</a></code> package, while the lazy
type is provided by the <code><a href="Data-Text.html#t:Lazy">Lazy</a></code> package. Internally, the
lazy <code>Text</code> type consists of a list of strict chunks.
</p><p>The strict <code><a href="Data-Text.html#t:Text">Text</a></code> type requires that an entire string fit into
memory at once. The lazy <code>Text</code> type is capable of streaming
strings that are larger than memory using a small memory footprint.
In many cases, the overhead of chunked streaming makes the lazy
<code>Text</code> type slower than its strict counterpart, but this is not
always the case. Sometimes, the time complexity of a function in
one module may be different from the other, due to their differing
internal structures.
</p><p>Each module provides an almost identical API, with the main
difference being that the strict module uses <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a></code> values for
lengths and counts, while the lazy module uses <code>Int64</code> lengths.
</p></div><h1 id="g:2">Acceptable data
</h1><div class="doc"><p>A <code><a href="Data-Text.html#t:Text">Text</a></code> value is a sequence of Unicode scalar values, as defined
in §3.9, definition D76 of the Unicode 5.2 standard:
<a href="http://www.unicode.org/versions/Unicode5.2.0/ch03.pdf#page=35">http://www.unicode.org/versions/Unicode5.2.0/ch03.pdf#page=35</a>. As
such, a <code><a href="Data-Text.html#t:Text">Text</a></code> cannot contain values in the range U+D800 to U+DFFF
inclusive. Haskell implementations admit all Unicode code points
(§3.4, definition D10) as <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></code> values, including code points
from this invalid range. This means that there are some <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></code>
values that are not valid Unicode scalar values, and the functions
in this module must handle those cases.
</p><p>Within this module, many functions construct a <code><a href="Data-Text.html#t:Text">Text</a></code> from one or
more <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></code> values. Those functions will substitute <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></code> values
that are not valid Unicode scalar values with the replacement
character "�" (U+FFFD). Functions that perform this
inspection and replacement are documented with the phrase
"Performs replacement on invalid scalar values".
</p><p>(One reason for this policy of replacement is that internally, a
<code><a href="Data-Text.html#t:Text">Text</a></code> value is represented as packed UTF-16 data. Values in the
range U+D800 through U+DFFF are used by UTF-16 to denote surrogate
code points, and so cannot be represented. The functions replace
invalid scalar values, instead of dropping them, as a security
measure. For details, see Unicode Technical Report 36, §3.5:
<a href="http://unicode.org/reports/tr36/#Deletion_of_Noncharacters">http://unicode.org/reports/tr36/#Deletion_of_Noncharacters</a>)
</p></div><h1 id="g:3">Fusion
</h1><div class="doc"><p>Most of the functions in this module are subject to <em>fusion</em>,
meaning that a pipeline of such functions will usually allocate at
most one <code><a href="Data-Text.html#t:Text">Text</a></code> value.
</p><p>As an example, consider the following pipeline:
</p><pre> import Data.Text as T
import Data.Text.Encoding as E
import Data.ByteString (ByteString)
countChars :: ByteString -> Int
countChars = T.length . T.toUpper . E.decodeUtf8
</pre><p>From the type signatures involved, this looks like it should
allocate one <code>ByteString</code> value, and two <code><a href="Data-Text.html#t:Text">Text</a></code> values. However,
when a module is compiled with optimisation enabled under GHC, the
two intermediate <code><a href="Data-Text.html#t:Text">Text</a></code> values will be optimised away, and the
function will be compiled down to a single loop over the source
<code>ByteString</code>.
</p><p>Functions that can be fused by the compiler are documented with the
phrase "Subject to fusion".
</p></div><h1 id="g:4">Types
</h1><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:Text" class="def">Text</a> <a href="src/Data-Text-Internal.html#Text" class="link">Source</a></p><div class="doc"><p>A space efficient, packed, unboxed Unicode text type.
</p></div><div class="subs instances"><p id="control.i:Text" class="caption collapser" onclick="toggleSection('i:Text')">Instances</p><div id="section.i:Text" class="show"><table><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Eq.html#t:Eq">Eq</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Data.html#t:Data">Data</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Ord.html#t:Ord">Ord</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Text-Read.html#t:Read">Read</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Text-Show.html#t:Show">Show</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Typeable-Internal.html#t:Typeable">Typeable</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-String.html#t:IsString">IsString</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Monoid.html#t:Monoid">Monoid</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/deepseq-1.3.0.0/Control-DeepSeq.html#t:NFData">NFData</a> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr></table></div></div></div><h1 id="g:5">Creation and elimination
</h1><div class="top"><p class="src"><a name="v:pack" class="def">pack</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-String.html#t:String">String</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#pack" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Convert a <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-String.html#t:String">String</a></code> into a <code><a href="Data-Text.html#t:Text">Text</a></code>. Subject to
fusion. Performs replacement on invalid scalar values.
</p></div></div><div class="top"><p class="src"><a name="v:unpack" class="def">unpack</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-String.html#t:String">String</a><a href="src/Data-Text.html#unpack" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Convert a Text into a String. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:singleton" class="def">singleton</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#singleton" class="link">Source</a></p><div class="doc"><p><em>O(1)</em> Convert a character into a Text. Subject to fusion.
Performs replacement on invalid scalar values.
</p></div></div><div class="top"><p class="src"><a name="v:empty" class="def">empty</a> :: <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text-Internal.html#empty" class="link">Source</a></p><div class="doc"><p><em>O(1)</em> The empty <code><a href="Data-Text.html#t:Text">Text</a></code>.
</p></div></div><h1 id="g:6">Basic interface
</h1><div class="top"><p class="src"><a name="v:cons" class="def">cons</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#cons" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Adds a character to the front of a <code><a href="Data-Text.html#t:Text">Text</a></code>. This function
is more costly than its <code>List</code> counterpart because it requires
copying a new array. Subject to fusion. Performs replacement on
invalid scalar values.
</p></div></div><div class="top"><p class="src"><a name="v:snoc" class="def">snoc</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#snoc" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Adds a character to the end of a <code><a href="Data-Text.html#t:Text">Text</a></code>. This copies the
entire array in the process, unless fused. Subject to fusion.
Performs replacement on invalid scalar values.
</p></div></div><div class="top"><p class="src"><a name="v:append" class="def">append</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#append" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Appends one <code><a href="Data-Text.html#t:Text">Text</a></code> to the other by copying both of them
into a new <code><a href="Data-Text.html#t:Text">Text</a></code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:uncons" class="def">uncons</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#uncons" class="link">Source</a></p><div class="doc"><p><em>O(1)</em> Returns the first character and rest of a <code><a href="Data-Text.html#t:Text">Text</a></code>, or
<code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#v:Nothing">Nothing</a></code> if empty. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:head" class="def">head</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#head" class="link">Source</a></p><div class="doc"><p><em>O(1)</em> Returns the first character of a <code><a href="Data-Text.html#t:Text">Text</a></code>, which must be
non-empty. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:last" class="def">last</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#last" class="link">Source</a></p><div class="doc"><p><em>O(1)</em> Returns the last character of a <code><a href="Data-Text.html#t:Text">Text</a></code>, which must be
non-empty. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:tail" class="def">tail</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#tail" class="link">Source</a></p><div class="doc"><p><em>O(1)</em> Returns all characters after the head of a <code><a href="Data-Text.html#t:Text">Text</a></code>, which
must be non-empty. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:init" class="def">init</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#init" class="link">Source</a></p><div class="doc"><p><em>O(1)</em> Returns all but the last character of a <code><a href="Data-Text.html#t:Text">Text</a></code>, which must
be non-empty. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:null" class="def">null</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a><a href="src/Data-Text.html#null" class="link">Source</a></p><div class="doc"><p><em>O(1)</em> Tests whether a <code><a href="Data-Text.html#t:Text">Text</a></code> is empty or not. Subject to
fusion.
</p></div></div><div class="top"><p class="src"><a name="v:length" class="def">length</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a><a href="src/Data-Text.html#length" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Returns the number of characters in a <code><a href="Data-Text.html#t:Text">Text</a></code>.
Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:compareLength" class="def">compareLength</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Ord.html#t:Ordering">Ordering</a><a href="src/Data-Text.html#compareLength" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Compare the count of characters in a <code><a href="Data-Text.html#t:Text">Text</a></code> to a number.
Subject to fusion.
</p><p>This function gives the same answer as comparing against the result
of <code><a href="Data-Text.html#v:length">length</a></code>, but can short circuit if the count of characters is
greater than the number, and hence be more efficient.
</p></div></div><h1 id="g:7">Transformations
</h1><div class="top"><p class="src"><a name="v:map" class="def">map</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#map" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:map">map</a></code> <code>f</code> <code>t</code> is the <code><a href="Data-Text.html#t:Text">Text</a></code> obtained by applying <code>f</code> to
each element of <code>t</code>. Subject to fusion. Performs replacement on
invalid scalar values.
</p></div></div><div class="top"><p class="src"><a name="v:intercalate" class="def">intercalate</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>] -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#intercalate" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> The <code><a href="Data-Text.html#v:intercalate">intercalate</a></code> function takes a <code><a href="Data-Text.html#t:Text">Text</a></code> and a list of
<code><a href="Data-Text.html#t:Text">Text</a></code>s and concatenates the list after interspersing the first
argument between each element of the list.
</p></div></div><div class="top"><p class="src"><a name="v:intersperse" class="def">intersperse</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#intersperse" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> The <code><a href="Data-Text.html#v:intersperse">intersperse</a></code> function takes a character and places it
between the characters of a <code><a href="Data-Text.html#t:Text">Text</a></code>. Subject to fusion. Performs
replacement on invalid scalar values.
</p></div></div><div class="top"><p class="src"><a name="v:transpose" class="def">transpose</a> :: [<a href="Data-Text.html#t:Text">Text</a>] -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#transpose" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> The <code><a href="Data-Text.html#v:transpose">transpose</a></code> function transposes the rows and columns
of its <code><a href="Data-Text.html#t:Text">Text</a></code> argument. Note that this function uses <code><a href="Data-Text.html#v:pack">pack</a></code>,
<code><a href="Data-Text.html#v:unpack">unpack</a></code>, and the list version of transpose, and is thus not very
efficient.
</p></div></div><div class="top"><p class="src"><a name="v:reverse" class="def">reverse</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#reverse" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Reverse the characters of a string. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:replace" class="def">replace</a><a href="src/Data-Text.html#replace" class="link">Source</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="Data-Text.html#t:Text">Text</a></td><td class="doc"><p>Text to search for
</p></td></tr><tr><td class="src">-> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc"><p>Replacement text
</p></td></tr><tr><td class="src">-> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc"><p>Input text
</p></td></tr><tr><td class="src">-> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc empty"> </td></tr></table></div><div class="doc"><p><em>O(m+n)</em> Replace every occurrence of one substring with another.
</p><p>In (unlikely) bad cases, this function's time complexity degrades
towards <em>O(n*m)</em>.
</p></div></div><h2 id="g:8">Case conversion
</h2><div class="doc"><p>When case converting <code><a href="Data-Text.html#t:Text">Text</a></code> values, do not use combinators like
<code>map toUpper</code> to case convert each character of a string
individually, as this gives incorrect results according to the
rules of some writing systems. The whole-string case conversion
functions from this module, such as <code>toUpper</code>, obey the correct
case conversion rules. As a result, these functions may map one
input character to two or three output characters. For examples,
see the documentation of each function.
</p><p><em>Note</em>: In some languages, case conversion is a locale- and
context-dependent operation. The case conversion functions in this
module are <em>not</em> locale sensitive. Programs that require locale
sensitivity should use appropriate versions of the case mapping
functions from the <code>text-icu</code> package:
<a href="http://hackage.haskell.org/package/text-icu">http://hackage.haskell.org/package/text-icu</a>
</p></div><div class="top"><p class="src"><a name="v:toCaseFold" class="def">toCaseFold</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#toCaseFold" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Convert a string to folded case. This function is mainly
useful for performing caseless (also known as case insensitive)
string comparisons.
</p><p>A string <code>x</code> is a caseless match for a string <code>y</code> if and only if:
</p><pre>toCaseFold x == toCaseFold y</pre><p>The result string may be longer than the input string, and may
differ from applying <code><a href="Data-Text.html#v:toLower">toLower</a></code> to the input string. For instance,
the Armenian small ligature "ﬓ" (men now, U+FB13) is case
folded to the sequence "մ" (men, U+0574) followed by
"ն" (now, U+0576), while the Greek "µ" (micro sign,
U+00B5) is case folded to "μ" (small letter mu, U+03BC)
instead of itself.
</p></div></div><div class="top"><p class="src"><a name="v:toLower" class="def">toLower</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#toLower" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Convert a string to lower case, using simple case
conversion. The result string may be longer than the input string.
For instance, "İ" (Latin capital letter I with dot above,
U+0130) maps to the sequence "i" (Latin small letter i, U+0069) followed
by " ̇" (combining dot above, U+0307).
</p></div></div><div class="top"><p class="src"><a name="v:toUpper" class="def">toUpper</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#toUpper" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Convert a string to upper case, using simple case
conversion. The result string may be longer than the input string.
For instance, the German "ß" (eszett, U+00DF) maps to the
two-letter sequence "SS".
</p></div></div><h2 id="g:9">Justification
</h2><div class="top"><p class="src"><a name="v:justifyLeft" class="def">justifyLeft</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#justifyLeft" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Left-justify a string to the given length, using the
specified fill character on the right. Subject to fusion.
Performs replacement on invalid scalar values.
</p><p>Examples:
</p><pre> justifyLeft 7 'x' "foo" == "fooxxxx"
justifyLeft 3 'x' "foobar" == "foobar"
</pre></div></div><div class="top"><p class="src"><a name="v:justifyRight" class="def">justifyRight</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#justifyRight" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Right-justify a string to the given length, using the
specified fill character on the left. Performs replacement on
invalid scalar values.
</p><p>Examples:
</p><pre> justifyRight 7 'x' "bar" == "xxxxbar"
justifyRight 3 'x' "foobar" == "foobar"
</pre></div></div><div class="top"><p class="src"><a name="v:center" class="def">center</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#center" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Center a string to the given length, using the specified
fill character on either side. Performs replacement on invalid
scalar values.
</p><p>Examples:
</p><pre> center 8 'x' "HS" = "xxxHSxxx"
</pre></div></div><h1 id="g:10">Folds
</h1><div class="top"><p class="src"><a name="v:foldl" class="def">foldl</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> a) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> a<a href="src/Data-Text.html#foldl" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:foldl">foldl</a></code>, applied to a binary operator, a starting value
(typically the left-identity of the operator), and a <code><a href="Data-Text.html#t:Text">Text</a></code>,
reduces the <code><a href="Data-Text.html#t:Text">Text</a></code> using the binary operator, from left to right.
Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:foldl-39-" class="def">foldl'</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> a) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> a<a href="src/Data-Text.html#foldl%27" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> A strict version of <code><a href="Data-Text.html#v:foldl">foldl</a></code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:foldl1" class="def">foldl1</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#foldl1" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> A variant of <code><a href="Data-Text.html#v:foldl">foldl</a></code> that has no starting value argument,
and thus must be applied to a non-empty <code><a href="Data-Text.html#t:Text">Text</a></code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:foldl1-39-" class="def">foldl1'</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#foldl1%27" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> A strict version of <code><a href="Data-Text.html#v:foldl1">foldl1</a></code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:foldr" class="def">foldr</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> a -> a) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> a<a href="src/Data-Text.html#foldr" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:foldr">foldr</a></code>, applied to a binary operator, a starting value
(typically the right-identity of the operator), and a <code><a href="Data-Text.html#t:Text">Text</a></code>,
reduces the <code><a href="Data-Text.html#t:Text">Text</a></code> using the binary operator, from right to left.
Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:foldr1" class="def">foldr1</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#foldr1" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> A variant of <code><a href="Data-Text.html#v:foldr">foldr</a></code> that has no starting value argument,
and thus must be applied to a non-empty <code><a href="Data-Text.html#t:Text">Text</a></code>. Subject to
fusion.
</p></div></div><h2 id="g:11">Special folds
</h2><div class="top"><p class="src"><a name="v:concat" class="def">concat</a> :: [<a href="Data-Text.html#t:Text">Text</a>] -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#concat" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Concatenate a list of <code><a href="Data-Text.html#t:Text">Text</a></code>s.
</p></div></div><div class="top"><p class="src"><a name="v:concatMap" class="def">concatMap</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#concatMap" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Map a function over a <code><a href="Data-Text.html#t:Text">Text</a></code> that results in a <code><a href="Data-Text.html#t:Text">Text</a></code>, and
concatenate the results.
</p></div></div><div class="top"><p class="src"><a name="v:any" class="def">any</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a><a href="src/Data-Text.html#any" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:any">any</a></code> <code>p</code> <code>t</code> determines whether any character in the
<code><a href="Data-Text.html#t:Text">Text</a></code> <code>t</code> satisifes the predicate <code>p</code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:all" class="def">all</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a><a href="src/Data-Text.html#all" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:all">all</a></code> <code>p</code> <code>t</code> determines whether all characters in the
<code><a href="Data-Text.html#t:Text">Text</a></code> <code>t</code> satisify the predicate <code>p</code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:maximum" class="def">maximum</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#maximum" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:maximum">maximum</a></code> returns the maximum value from a <code><a href="Data-Text.html#t:Text">Text</a></code>, which
must be non-empty. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:minimum" class="def">minimum</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#minimum" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:minimum">minimum</a></code> returns the minimum value from a <code><a href="Data-Text.html#t:Text">Text</a></code>, which
must be non-empty. Subject to fusion.
</p></div></div><h1 id="g:12">Construction
</h1><h2 id="g:13">Scans
</h2><div class="top"><p class="src"><a name="v:scanl" class="def">scanl</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#scanl" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:scanl">scanl</a></code> is similar to <code><a href="Data-Text.html#v:foldl">foldl</a></code>, but returns a list of
successive reduced values from the left. Subject to fusion.
Performs replacement on invalid scalar values.
</p><pre> scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]
</pre><p>Note that
</p><pre> last (scanl f z xs) == foldl f z xs.
</pre></div></div><div class="top"><p class="src"><a name="v:scanl1" class="def">scanl1</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#scanl1" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:scanl1">scanl1</a></code> is a variant of <code><a href="Data-Text.html#v:scanl">scanl</a></code> that has no starting
value argument. Subject to fusion. Performs replacement on
invalid scalar values.
</p><pre> scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]
</pre></div></div><div class="top"><p class="src"><a name="v:scanr" class="def">scanr</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#scanr" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:scanr">scanr</a></code> is the right-to-left dual of <code><a href="Data-Text.html#v:scanl">scanl</a></code>. Performs
replacement on invalid scalar values.
</p><pre> scanr f v == reverse . scanl (flip f) v . reverse
</pre></div></div><div class="top"><p class="src"><a name="v:scanr1" class="def">scanr1</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#scanr1" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:scanr1">scanr1</a></code> is a variant of <code><a href="Data-Text.html#v:scanr">scanr</a></code> that has no starting
value argument. Subject to fusion. Performs replacement on
invalid scalar values.
</p></div></div><h2 id="g:14">Accumulating maps
</h2><div class="top"><p class="src"><a name="v:mapAccumL" class="def">mapAccumL</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> (a, <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>)) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> (a, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#mapAccumL" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Like a combination of <code><a href="Data-Text.html#v:map">map</a></code> and <code><a href="Data-Text.html#v:foldl-39-">foldl'</a></code>. Applies a
function to each element of a <code><a href="Data-Text.html#t:Text">Text</a></code>, passing an accumulating
parameter from left to right, and returns a final <code><a href="Data-Text.html#t:Text">Text</a></code>. Performs
replacement on invalid scalar values.
</p></div></div><div class="top"><p class="src"><a name="v:mapAccumR" class="def">mapAccumR</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> (a, <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>)) -> a -> <a href="Data-Text.html#t:Text">Text</a> -> (a, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#mapAccumR" class="link">Source</a></p><div class="doc"><p>The <code><a href="Data-Text.html#v:mapAccumR">mapAccumR</a></code> function behaves like a combination of <code><a href="Data-Text.html#v:map">map</a></code> and
a strict <code><a href="Data-Text.html#v:foldr">foldr</a></code>; it applies a function to each element of a
<code><a href="Data-Text.html#t:Text">Text</a></code>, passing an accumulating parameter from right to left, and
returning a final value of this accumulator together with the new
<code><a href="Data-Text.html#t:Text">Text</a></code>.
Performs replacement on invalid scalar values.
</p></div></div><h2 id="g:15">Generation and unfolding
</h2><div class="top"><p class="src"><a name="v:replicate" class="def">replicate</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#replicate" class="link">Source</a></p><div class="doc"><p><em>O(n*m)</em> <code><a href="Data-Text.html#v:replicate">replicate</a></code> <code>n</code> <code>t</code> is a <code><a href="Data-Text.html#t:Text">Text</a></code> consisting of the input
<code>t</code> repeated <code>n</code> times.
</p></div></div><div class="top"><p class="src"><a name="v:unfoldr" class="def">unfoldr</a> :: (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>, a)) -> a -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#unfoldr" class="link">Source</a></p><div class="doc"><p><em>O(n)</em>, where <code>n</code> is the length of the result. The <code><a href="Data-Text.html#v:unfoldr">unfoldr</a></code>
function is analogous to the List <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-List.html#v:unfoldr">unfoldr</a></code>. <code><a href="Data-Text.html#v:unfoldr">unfoldr</a></code> builds a
<code><a href="Data-Text.html#t:Text">Text</a></code> from a seed value. The function takes the element and
returns <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#v:Nothing">Nothing</a></code> if it is done producing the <code><a href="Data-Text.html#t:Text">Text</a></code>, otherwise
<code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#v:Just">Just</a></code> <code>(a,b)</code>. In this case, <code>a</code> is the next <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></code> in the
string, and <code>b</code> is the seed value for further production. Subject
to fusion. Performs replacement on invalid scalar values.
</p></div></div><div class="top"><p class="src"><a name="v:unfoldrN" class="def">unfoldrN</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> (a -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>, a)) -> a -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#unfoldrN" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Like <code><a href="Data-Text.html#v:unfoldr">unfoldr</a></code>, <code><a href="Data-Text.html#v:unfoldrN">unfoldrN</a></code> builds a <code><a href="Data-Text.html#t:Text">Text</a></code> from a seed
value. However, the length of the result should be limited by the
first argument to <code><a href="Data-Text.html#v:unfoldrN">unfoldrN</a></code>. This function is more efficient than
<code><a href="Data-Text.html#v:unfoldr">unfoldr</a></code> when the maximum length of the result is known and
correct, otherwise its performance is similar to <code><a href="Data-Text.html#v:unfoldr">unfoldr</a></code>. Subject
to fusion. Performs replacement on invalid scalar values.
</p></div></div><h1 id="g:16">Substrings
</h1><h2 id="g:17">Breaking strings
</h2><div class="top"><p class="src"><a name="v:take" class="def">take</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#take" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:take">take</a></code> <code>n</code>, applied to a <code><a href="Data-Text.html#t:Text">Text</a></code>, returns the prefix of the
<code><a href="Data-Text.html#t:Text">Text</a></code> of length <code>n</code>, or the <code><a href="Data-Text.html#t:Text">Text</a></code> itself if <code>n</code> is greater than
the length of the Text. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:drop" class="def">drop</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#drop" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:drop">drop</a></code> <code>n</code>, applied to a <code><a href="Data-Text.html#t:Text">Text</a></code>, returns the suffix of the
<code><a href="Data-Text.html#t:Text">Text</a></code> after the first <code>n</code> characters, or the empty <code><a href="Data-Text.html#t:Text">Text</a></code> if <code>n</code>
is greater than the length of the <code><a href="Data-Text.html#t:Text">Text</a></code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:takeWhile" class="def">takeWhile</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#takeWhile" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:takeWhile">takeWhile</a></code>, applied to a predicate <code>p</code> and a <code><a href="Data-Text.html#t:Text">Text</a></code>,
returns the longest prefix (possibly empty) of elements that
satisfy <code>p</code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:dropWhile" class="def">dropWhile</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#dropWhile" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:dropWhile">dropWhile</a></code> <code>p</code> <code>t</code> returns the suffix remaining after
<code><a href="Data-Text.html#v:takeWhile">takeWhile</a></code> <code>p</code> <code>t</code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:dropWhileEnd" class="def">dropWhileEnd</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#dropWhileEnd" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:dropWhileEnd">dropWhileEnd</a></code> <code>p</code> <code>t</code> returns the prefix remaining after
dropping characters that fail the predicate <code>p</code> from the end of
<code>t</code>. Subject to fusion.
Examples:
</p><pre> dropWhileEnd (=='.') "foo..." == "foo"
</pre></div></div><div class="top"><p class="src"><a name="v:dropAround" class="def">dropAround</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#dropAround" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:dropAround">dropAround</a></code> <code>p</code> <code>t</code> returns the substring remaining after
dropping characters that fail the predicate <code>p</code> from both the
beginning and end of <code>t</code>. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:strip" class="def">strip</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#strip" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Remove leading and trailing white space from a string.
Equivalent to:
</p><pre> dropAround isSpace
</pre></div></div><div class="top"><p class="src"><a name="v:stripStart" class="def">stripStart</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#stripStart" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Remove leading white space from a string. Equivalent to:
</p><pre> dropWhile isSpace
</pre></div></div><div class="top"><p class="src"><a name="v:stripEnd" class="def">stripEnd</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#stripEnd" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Remove trailing white space from a string. Equivalent to:
</p><pre> dropWhileEnd isSpace
</pre></div></div><div class="top"><p class="src"><a name="v:splitAt" class="def">splitAt</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#splitAt" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:splitAt">splitAt</a></code> <code>n t</code> returns a pair whose first element is a
prefix of <code>t</code> of length <code>n</code>, and whose second is the remainder of
the string. It is equivalent to <code>(<code><a href="Data-Text.html#v:take">take</a></code> n t, <code><a href="Data-Text.html#v:drop">drop</a></code> n t)</code>.
</p></div></div><div class="top"><p class="src"><a name="v:breakOn" class="def">breakOn</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#breakOn" class="link">Source</a></p><div class="doc"><p><em>O(n+m)</em> Find the first instance of <code>needle</code> (which must be
non-<code><a href="Data-Text.html#v:null">null</a></code>) in <code>haystack</code>. The first element of the returned tuple
is the prefix of <code>haystack</code> before <code>needle</code> is matched. The second
is the remainder of <code>haystack</code>, starting with the match.
</p><p>Examples:
</p><pre> breakOn "::" "a::b::c" ==> ("a", "::b::c")
breakOn "/" "foobar" ==> ("foobar", "")
</pre><p>Laws:
</p><pre> append prefix match == haystack
where (prefix, match) = breakOn needle haystack
</pre><p>If you need to break a string by a substring repeatedly (e.g. you
want to break on every instance of a substring), use <code><a href="Data-Text.html#v:breakOnAll">breakOnAll</a></code>
instead, as it has lower startup overhead.
</p><p>In (unlikely) bad cases, this function's time complexity degrades
towards <em>O(n*m)</em>.
</p></div></div><div class="top"><p class="src"><a name="v:breakOnEnd" class="def">breakOnEnd</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#breakOnEnd" class="link">Source</a></p><div class="doc"><p><em>O(n+m)</em> Similar to <code><a href="Data-Text.html#v:breakOn">breakOn</a></code>, but searches from the end of the
string.
</p><p>The first element of the returned tuple is the prefix of <code>haystack</code>
up to and including the last match of <code>needle</code>. The second is the
remainder of <code>haystack</code>, following the match.
</p><pre> breakOnEnd "::" "a::b::c" ==> ("a::b::", "c")
</pre></div></div><div class="top"><p class="src"><a name="v:break" class="def">break</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#break" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:break">break</a></code> is like <code><a href="Data-Text.html#v:span">span</a></code>, but the prefix returned is
over elements that fail the predicate <code>p</code>.
</p></div></div><div class="top"><p class="src"><a name="v:span" class="def">span</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#span" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:span">span</a></code>, applied to a predicate <code>p</code> and text <code>t</code>, returns
a pair whose first element is the longest prefix (possibly empty)
of <code>t</code> of elements that satisfy <code>p</code>, and whose second is the
remainder of the list.
</p></div></div><div class="top"><p class="src"><a name="v:group" class="def">group</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#group" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Group characters in a string by equality.
</p></div></div><div class="top"><p class="src"><a name="v:groupBy" class="def">groupBy</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#groupBy" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Group characters in a string according to a predicate.
</p></div></div><div class="top"><p class="src"><a name="v:inits" class="def">inits</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#inits" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Return all initial segments of the given <code><a href="Data-Text.html#t:Text">Text</a></code>, shortest
first.
</p></div></div><div class="top"><p class="src"><a name="v:tails" class="def">tails</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#tails" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Return all final segments of the given <code><a href="Data-Text.html#t:Text">Text</a></code>, longest
first.
</p></div></div><h2 id="g:18">Breaking into many substrings
</h2><div class="doc"><p>Splitting functions in this library do not perform character-wise
copies to create substrings; they just construct new <code><a href="Data-Text.html#t:Text">Text</a></code>s that
are slices of the original.
</p></div><div class="top"><p class="src"><a name="v:splitOn" class="def">splitOn</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#splitOn" class="link">Source</a></p><div class="doc"><p><em>O(m+n)</em> Break a <code><a href="Data-Text.html#t:Text">Text</a></code> into pieces separated by the first
<code><a href="Data-Text.html#t:Text">Text</a></code> argument, consuming the delimiter. An empty delimiter is
invalid, and will cause an error to be raised.
</p><p>Examples:
</p><pre> splitOn "\r\n" "a\r\nb\r\nd\r\ne" == ["a","b","d","e"]
splitOn "aaa" "aaaXaaaXaaaXaaa" == ["","X","X","X",""]
splitOn "x" "x" == ["",""]
</pre><p>and
</p><pre> intercalate s . splitOn s == id
splitOn (singleton c) == split (==c)
</pre><p>In (unlikely) bad cases, this function's time complexity degrades
towards <em>O(n*m)</em>.
</p></div></div><div class="top"><p class="src"><a name="v:split" class="def">split</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#split" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Splits a <code><a href="Data-Text.html#t:Text">Text</a></code> into components delimited by separators,
where the predicate returns True for a separator element. The
resulting components do not contain the separators. Two adjacent
separators result in an empty component in the output. eg.
</p><pre> split (=='a') "aabbaca" == ["","","bb","c",""]
split (=='a') "" == [""]
</pre></div></div><div class="top"><p class="src"><a name="v:chunksOf" class="def">chunksOf</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#chunksOf" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Splits a <code><a href="Data-Text.html#t:Text">Text</a></code> into components of length <code>k</code>. The last
element may be shorter than the other chunks, depending on the
length of the input. Examples:
</p><pre> chunksOf 3 "foobarbaz" == ["foo","bar","baz"]
chunksOf 4 "haskell.org" == ["hask","ell.","org"]
</pre></div></div><h2 id="g:19">Breaking into lines and words
</h2><div class="top"><p class="src"><a name="v:lines" class="def">lines</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#lines" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Breaks a <code><a href="Data-Text.html#t:Text">Text</a></code> up into a list of <code><a href="Data-Text.html#t:Text">Text</a></code>s at
newline <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></code>s. The resulting strings do not contain newlines.
</p></div></div><div class="top"><p class="src"><a name="v:words" class="def">words</a> :: <a href="Data-Text.html#t:Text">Text</a> -> [<a href="Data-Text.html#t:Text">Text</a>]<a href="src/Data-Text.html#words" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Breaks a <code><a href="Data-Text.html#t:Text">Text</a></code> up into a list of words, delimited by <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></code>s
representing white space.
</p></div></div><div class="top"><p class="src"><a name="v:unlines" class="def">unlines</a> :: [<a href="Data-Text.html#t:Text">Text</a>] -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#unlines" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Joins lines, after appending a terminating newline to
each.
</p></div></div><div class="top"><p class="src"><a name="v:unwords" class="def">unwords</a> :: [<a href="Data-Text.html#t:Text">Text</a>] -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#unwords" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Joins words using single space characters.
</p></div></div><h1 id="g:20">Predicates
</h1><div class="top"><p class="src"><a name="v:isPrefixOf" class="def">isPrefixOf</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a><a href="src/Data-Text.html#isPrefixOf" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> The <code><a href="Data-Text.html#v:isPrefixOf">isPrefixOf</a></code> function takes two <code><a href="Data-Text.html#t:Text">Text</a></code>s and returns
<code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#v:True">True</a></code> iff the first is a prefix of the second. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:isSuffixOf" class="def">isSuffixOf</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a><a href="src/Data-Text.html#isSuffixOf" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> The <code><a href="Data-Text.html#v:isSuffixOf">isSuffixOf</a></code> function takes two <code><a href="Data-Text.html#t:Text">Text</a></code>s and returns
<code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#v:True">True</a></code> iff the first is a suffix of the second.
</p></div></div><div class="top"><p class="src"><a name="v:isInfixOf" class="def">isInfixOf</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a><a href="src/Data-Text.html#isInfixOf" class="link">Source</a></p><div class="doc"><p><em>O(n+m)</em> The <code><a href="Data-Text.html#v:isInfixOf">isInfixOf</a></code> function takes two <code><a href="Data-Text.html#t:Text">Text</a></code>s and returns
<code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#v:True">True</a></code> iff the first is contained, wholly and intact, anywhere
within the second.
</p><p>In (unlikely) bad cases, this function's time complexity degrades
towards <em>O(n*m)</em>.
</p></div></div><h2 id="g:21">View patterns
</h2><div class="top"><p class="src"><a name="v:stripPrefix" class="def">stripPrefix</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#stripPrefix" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Return the suffix of the second string if its prefix
matches the entire first string.
</p><p>Examples:
</p><pre> stripPrefix "foo" "foobar" == Just "bar"
stripPrefix "" "baz" == Just "baz"
stripPrefix "foo" "quux" == Nothing
</pre><p>This is particularly useful with the <code>ViewPatterns</code> extension to
GHC, as follows:
</p><pre> {-# LANGUAGE ViewPatterns #-}
import Data.Text as T
fnordLength :: Text -> Int
fnordLength (stripPrefix "fnord" -> Just suf) = T.length suf
fnordLength _ = -1
</pre></div></div><div class="top"><p class="src"><a name="v:stripSuffix" class="def">stripSuffix</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#stripSuffix" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Return the prefix of the second string if its suffix
matches the entire first string.
</p><p>Examples:
</p><pre> stripSuffix "bar" "foobar" == Just "foo"
stripSuffix "" "baz" == Just "baz"
stripSuffix "foo" "quux" == Nothing
</pre><p>This is particularly useful with the <code>ViewPatterns</code> extension to
GHC, as follows:
</p><pre> {-# LANGUAGE ViewPatterns #-}
import Data.Text as T
quuxLength :: Text -> Int
quuxLength (stripSuffix "quux" -> Just pre) = T.length pre
quuxLength _ = -1
</pre></div></div><div class="top"><p class="src"><a name="v:commonPrefixes" class="def">commonPrefixes</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#commonPrefixes" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> Find the longest non-empty common prefix of two strings
and return it, along with the suffixes of each string at which they
no longer match.
</p><p>If the strings do not have a common prefix or either one is empty,
this function returns <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#v:Nothing">Nothing</a></code>.
</p><p>Examples:
</p><pre> commonPrefixes "foobar" "fooquux" == Just ("foo","bar","quux")
commonPrefixes "veeble" "fetzer" == Nothing
commonPrefixes "" "baz" == Nothing
</pre></div></div><h1 id="g:22">Searching
</h1><div class="top"><p class="src"><a name="v:filter" class="def">filter</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#filter" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:filter">filter</a></code>, applied to a predicate and a <code><a href="Data-Text.html#t:Text">Text</a></code>,
returns a <code><a href="Data-Text.html#t:Text">Text</a></code> containing those characters that satisfy the
predicate.
</p></div></div><div class="top"><p class="src"><a name="v:breakOnAll" class="def">breakOnAll</a><a href="src/Data-Text.html#breakOnAll" class="link">Source</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="Data-Text.html#t:Text">Text</a></td><td class="doc"><p><code>needle</code> to search for
</p></td></tr><tr><td class="src">-> <a href="Data-Text.html#t:Text">Text</a></td><td class="doc"><p><code>haystack</code> in which to search
</p></td></tr><tr><td class="src">-> [(<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)]</td><td class="doc empty"> </td></tr></table></div><div class="doc"><p><em>O(n+m)</em> Find all non-overlapping instances of <code>needle</code> in
<code>haystack</code>. Each element of the returned list consists of a pair:
</p><ul><li> The entire string prior to the <em>k</em>th match (i.e. the prefix)
</li><li> The <em>k</em>th match, followed by the remainder of the string
</li></ul><p>Examples:
</p><pre> breakOnAll "::" ""
==> []
breakOnAll "/" "a/b/c/"
==> [("a", "/b/c/"), ("a/b", "/c/"), ("a/b/c", "/")]
</pre><p>In (unlikely) bad cases, this function's time complexity degrades
towards <em>O(n*m)</em>.
</p><p>The <code>needle</code> parameter may not be empty.
</p></div></div><div class="top"><p class="src"><a name="v:find" class="def">find</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#find" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> The <code><a href="Data-Text.html#v:find">find</a></code> function takes a predicate and a <code><a href="Data-Text.html#t:Text">Text</a></code>, and
returns the first element matching the predicate, or <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#v:Nothing">Nothing</a></code> if
there is no such element.
</p></div></div><div class="top"><p class="src"><a name="v:partition" class="def">partition</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> (<a href="Data-Text.html#t:Text">Text</a>, <a href="Data-Text.html#t:Text">Text</a>)<a href="src/Data-Text.html#partition" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> The <code><a href="Data-Text.html#v:partition">partition</a></code> function takes a predicate and a <code><a href="Data-Text.html#t:Text">Text</a></code>,
and returns the pair of <code><a href="Data-Text.html#t:Text">Text</a></code>s with elements which do and do not
satisfy the predicate, respectively; i.e.
</p><pre> partition p t == (filter p t, filter (not . p) t)
</pre></div></div><h1 id="g:23">Indexing
</h1><div class="doc"><p>If you think of a <code><a href="Data-Text.html#t:Text">Text</a></code> value as an array of <code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a></code> values (which
it is not), you run the risk of writing inefficient code.
</p><p>An idiom that is common in some languages is to find the numeric
offset of a character or substring, then use that number to split
or trim the searched string. With a <code><a href="Data-Text.html#t:Text">Text</a></code> value, this approach
would require two <em>O(n)</em> operations: one to perform the search, and
one to operate from wherever the search ended.
</p><p>For example, suppose you have a string that you want to split on
the substring <code>"::"</code>, such as <code>"foo::bar::quux"</code>. Instead of
searching for the index of <code>"::"</code> and taking the substrings
before and after that index, you would instead use <code>breakOnAll "::"</code>.
</p></div><div class="top"><p class="src"><a name="v:index" class="def">index</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a><a href="src/Data-Text.html#index" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#t:Text">Text</a></code> index (subscript) operator, starting from 0.
</p></div></div><div class="top"><p class="src"><a name="v:findIndex" class="def">findIndex</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a><a href="src/Data-Text.html#findIndex" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> The <code><a href="Data-Text.html#v:findIndex">findIndex</a></code> function takes a predicate and a <code><a href="Data-Text.html#t:Text">Text</a></code>
and returns the index of the first element in the <code><a href="Data-Text.html#t:Text">Text</a></code> satisfying
the predicate. Subject to fusion.
</p></div></div><div class="top"><p class="src"><a name="v:count" class="def">count</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Int.html#t:Int">Int</a><a href="src/Data-Text.html#count" class="link">Source</a></p><div class="doc"><p><em>O(n+m)</em> The <code><a href="Data-Text.html#v:count">count</a></code> function returns the number of times the
query string appears in the given <code><a href="Data-Text.html#t:Text">Text</a></code>. An empty query string is
invalid, and will cause an error to be raised.
</p><p>In (unlikely) bad cases, this function's time complexity degrades
towards <em>O(n*m)</em>.
</p></div></div><h1 id="g:24">Zipping and unzipping
</h1><div class="top"><p class="src"><a name="v:zip" class="def">zip</a> :: <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> [(<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>, <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>)]<a href="src/Data-Text.html#zip" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:zip">zip</a></code> takes two <code><a href="Data-Text.html#t:Text">Text</a></code>s and returns a list of
corresponding pairs of bytes. If one input <code><a href="Data-Text.html#t:Text">Text</a></code> is short,
excess elements of the longer <code><a href="Data-Text.html#t:Text">Text</a></code> are discarded. This is
equivalent to a pair of <code><a href="Data-Text.html#v:unpack">unpack</a></code> operations.
</p></div></div><div class="top"><p class="src"><a name="v:zipWith" class="def">zipWith</a> :: (<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a> -> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.5.0.0/Data-Char.html#t:Char">Char</a>) -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a> -> <a href="Data-Text.html#t:Text">Text</a><a href="src/Data-Text.html#zipWith" class="link">Source</a></p><div class="doc"><p><em>O(n)</em> <code><a href="Data-Text.html#v:zipWith">zipWith</a></code> generalises <code><a href="Data-Text.html#v:zip">zip</a></code> by zipping with the function
given as the first argument, instead of a tupling function.
Performs replacement on invalid scalar values.
</p></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.10.0</p></div></body></html>
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