/usr/share/doc/ruby-gsl/examples/vector/collect.rb is in ruby-gsl 2.1.0.3+dfsg1-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | #!/usr/bin/env ruby
# Turn on warnings
$-w = true
require 'irb/xmp'
require 'gsl'
# Apparently, IRB::Frame has a bug that prevents the defaults from working, so
# an XMP instance must be created explicitly this way instead of using the
# otherwise convenient xmp method.
XMP.new(IRB::Frame.top(-1)).puts <<END
# Create Vector v
v = GSL::Vector::Int[0..5]
# Create new Vector whose elements are squares of v's elements
v.collect { |a| a*a }
# Show that v us unmodified
v
# Square elements of v in-place
v.collect! { |a| a*a }
# Show that v is modified
v
END
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