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[1X6 [33X[0;0YManipulating Codes[133X[101X
[33X[0;0YIn this chapter we describe several functions [5XGUAVA[105X uses to manipulate
codes. Some of the best codes are obtained by starting with for example a
BCH code, and manipulating it.[133X
[33X[0;0YIn some cases, it is faster to perform calculations with a manipulated code
than to use the original code. For example, if the dimension of the code is
larger than half the word length, it is generally faster to compute the
weight distribution by first calculating the weight distribution of the dual
code than by directly calculating the weight distribution of the original
code. The size of the dual code is smaller in these cases.[133X
[33X[0;0YBecause [5XGUAVA[105X keeps all information in a code record, in some cases the
information can be preserved after manipulations. Therefore, computations do
not always have to start from scratch.[133X
[33X[0;0YIn Section [14X6.1[114X, we describe functions that take a code with certain
parameters, modify it in some way and return a different code (see
[2XExtendedCode[102X ([14X6.1-1[114X), [2XPuncturedCode[102X ([14X6.1-2[114X), [2XEvenWeightSubcode[102X ([14X6.1-3[114X),
[2XPermutedCode[102X ([14X6.1-4[114X), [2XExpurgatedCode[102X ([14X6.1-5[114X), [2XAugmentedCode[102X ([14X6.1-6[114X),
[2XRemovedElementsCode[102X ([14X6.1-7[114X), [2XAddedElementsCode[102X ([14X6.1-8[114X), [2XShortenedCode[102X
([14X6.1-9[114X), [2XLengthenedCode[102X ([14X6.1-10[114X), [2XResidueCode[102X ([14X6.1-12[114X), [2XConstructionBCode[102X
([14X6.1-13[114X), [2XDualCode[102X ([14X6.1-14[114X), [2XConversionFieldCode[102X ([14X6.1-15[114X),
[2XConstantWeightSubcode[102X ([14X6.1-18[114X), [2XStandardFormCode[102X ([14X6.1-19[114X) and [2XCosetCode[102X
([14X6.1-17[114X)). In Section [14X6.2[114X, we describe functions that generate a new code
out of two codes (see [2XDirectSumCode[102X ([14X6.2-1[114X), [2XUUVCode[102X ([14X6.2-2[114X),
[2XDirectProductCode[102X ([14X6.2-3[114X), [2XIntersectionCode[102X ([14X6.2-4[114X) and [2XUnionCode[102X ([14X6.2-5[114X)).[133X
[1X6.1 [33X[0;0YFunctions that Generate a New Code from a Given Code[133X[101X
[1X6.1-1 ExtendedCode[101X
[29X[2XExtendedCode[102X( [3XC[103X[, [3Xi[103X] ) [32X function
[33X[0;0Y[10XExtendedCode[110X extends the code [3XC[103X [3Xi[103X times and returns the result. [3Xi[103X is equal
to [22X1[122X by default. Extending is done by adding a parity check bit after the
last coordinate. The coordinates of all codewords now add up to zero. In the
binary case, each codeword has even weight.[133X
[33X[0;0YThe word length increases by [3Xi[103X. The size of the code remains the same. In
the binary case, the minimum distance increases by one if it was odd. In
other cases, that is not always true.[133X
[33X[0;0YA cyclic code in general is no longer cyclic after extending.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := HammingCode( 3, GF(2) );[127X[104X
[4X[28Xa linear [7,4,3]1 Hamming (3,2) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 := ExtendedCode( C1 );[127X[104X
[4X[28Xa linear [8,4,4]2 extended code[128X[104X
[4X[25Xgap>[125X [27XIsEquivalent( C2, ReedMullerCode( 1, 3 ) );[127X[104X
[4X[28Xtrue[128X[104X
[4X[25Xgap>[125X [27XList( AsSSortedList( C2 ), WeightCodeword );[127X[104X
[4X[28X[ 0, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 8 ][128X[104X
[4X[25Xgap>[125X [27XC3 := EvenWeightSubcode( C1 );[127X[104X
[4X[28Xa linear [7,3,4]2..3 even weight subcode [128X[104X
[4X[32X[104X
[33X[0;0YTo undo extending, call [10XPuncturedCode[110X (see [2XPuncturedCode[102X ([14X6.1-2[114X)). The
function [10XEvenWeightSubcode[110X (see [2XEvenWeightSubcode[102X ([14X6.1-3[114X)) also returns a
related code with only even weights, but without changing its word length.[133X
[1X6.1-2 PuncturedCode[101X
[29X[2XPuncturedCode[102X( [3XC[103X ) [32X function
[33X[0;0Y[10XPuncturedCode[110X punctures [3XC[103X in the last column, and returns the result.
Puncturing is done simply by cutting off the last column from each codeword.
This means the word length decreases by one. The minimum distance in general
also decrease by one.[133X
[33X[0;0YThis command can also be called with the syntax [10XPuncturedCode( C, L )[110X. In
this case, [10XPuncturedCode[110X punctures [3XC[103X in the columns specified by [3XL[103X, a list
of integers. All columns specified by [3XL[103X are omitted from each codeword. If [22Xl[122X
is the length of [3XL[103X (so the number of removed columns), the word length
decreases by [22Xl[122X. The minimum distance can also decrease by [22Xl[122X or less.[133X
[33X[0;0YPuncturing a cyclic code in general results in a non-cyclic code. If the
code is punctured in all the columns where a word of minimal weight is
unequal to zero, the dimension of the resulting code decreases.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := BCHCode( 15, 5, GF(2) );[127X[104X
[4X[28Xa cyclic [15,7,5]3..5 BCH code, delta=5, b=1 over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 := PuncturedCode( C1 );[127X[104X
[4X[28Xa linear [14,7,4]3..5 punctured code[128X[104X
[4X[25Xgap>[125X [27XExtendedCode( C2 ) = C1;[127X[104X
[4X[28Xfalse[128X[104X
[4X[25Xgap>[125X [27XPuncturedCode( C1, [1,2,3,4,5,6,7] );[127X[104X
[4X[28Xa linear [8,7,1]1 punctured code[128X[104X
[4X[25Xgap>[125X [27XPuncturedCode( WholeSpaceCode( 4, GF(5) ) );[127X[104X
[4X[28Xa linear [3,3,1]0 punctured code # The dimension decreased from 4 to 3 [128X[104X
[4X[32X[104X
[33X[0;0Y[10XExtendedCode[110X extends the code again (see [2XExtendedCode[102X ([14X6.1-1[114X)), although in
general this does not result in the old code.[133X
[1X6.1-3 EvenWeightSubcode[101X
[29X[2XEvenWeightSubcode[102X( [3XC[103X ) [32X function
[33X[0;0Y[10XEvenWeightSubcode[110X returns the even weight subcode of [3XC[103X, consisting of all
codewords of [3XC[103X with even weight. If [3XC[103X is a linear code and contains words of
odd weight, the resulting code has a dimension of one less. The minimum
distance always increases with one if it was odd. If [3XC[103X is a binary cyclic
code, and [22Xg(x)[122X is its generator polynomial, the even weight subcode either
has generator polynomial [22Xg(x)[122X (if [22Xg(x)[122X is divisible by [22Xx-1[122X) or [22Xg(x)⋅ (x-1)[122X
(if no factor [22Xx-1[122X was present in [22Xg(x)[122X). So the even weight subcode is again
cyclic.[133X
[33X[0;0YOf course, if all codewords of [3XC[103X are already of even weight, the returned
code is equal to [3XC[103X.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := EvenWeightSubcode( BCHCode( 8, 4, GF(3) ) );[127X[104X
[4X[28Xan (8,33,4..8)3..8 even weight subcode[128X[104X
[4X[25Xgap>[125X [27XList( AsSSortedList( C1 ), WeightCodeword );[127X[104X
[4X[28X[ 0, 4, 4, 4, 4, 4, 4, 6, 4, 4, 4, 4, 6, 4, 4, 6, 4, 4, 8, 6, 4, 6, 8, 4, 4, [128X[104X
[4X[28X 4, 6, 4, 6, 8, 4, 6, 8 ][128X[104X
[4X[25Xgap>[125X [27XEvenWeightSubcode( ReedMullerCode( 1, 3 ) );[127X[104X
[4X[28Xa linear [8,4,4]2 Reed-Muller (1,3) code over GF(2) [128X[104X
[4X[32X[104X
[33X[0;0Y[10XExtendedCode[110X also returns a related code of only even weights, but without
reducing its dimension (see [2XExtendedCode[102X ([14X6.1-1[114X)).[133X
[1X6.1-4 PermutedCode[101X
[29X[2XPermutedCode[102X( [3XC[103X, [3XL[103X ) [32X function
[33X[0;0Y[10XPermutedCode[110X returns [3XC[103X after column permutations. [3XL[103X (in GAP disjoint cycle
notation) is the permutation to be executed on the columns of [3XC[103X. If [3XC[103X is
cyclic, the result in general is no longer cyclic. If a permutation results
in the same code as [3XC[103X, this permutation belongs to the automorphism group of
[3XC[103X (see [2XAutomorphismGroup[102X ([14X4.4-3[114X)). In any case, the returned code is
equivalent to [3XC[103X (see [2XIsEquivalent[102X ([14X4.4-1[114X)).[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := PuncturedCode( ReedMullerCode( 1, 4 ) );[127X[104X
[4X[28Xa linear [15,5,7]5 punctured code[128X[104X
[4X[25Xgap>[125X [27XC2 := BCHCode( 15, 7, GF(2) );[127X[104X
[4X[28Xa cyclic [15,5,7]5 BCH code, delta=7, b=1 over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 = C1;[127X[104X
[4X[28Xfalse[128X[104X
[4X[25Xgap>[125X [27Xp := CodeIsomorphism( C1, C2 );[127X[104X
[4X[28X( 2, 4,14, 9,13, 7,11,10, 6, 8,12, 5)[128X[104X
[4X[25Xgap>[125X [27XC3 := PermutedCode( C1, p );[127X[104X
[4X[28Xa linear [15,5,7]5 permuted code[128X[104X
[4X[25Xgap>[125X [27XC2 = C3;[127X[104X
[4X[28Xtrue [128X[104X
[4X[32X[104X
[1X6.1-5 ExpurgatedCode[101X
[29X[2XExpurgatedCode[102X( [3XC[103X, [3XL[103X ) [32X function
[33X[0;0Y[10XExpurgatedCode[110X expurgates the code [3XC[103X> by throwing away codewords in list [3XL[103X.
[3XC[103X must be a linear code. [3XL[103X must be a list of codeword input. The generator
matrix of the new code no longer is a basis for the codewords specified by
[3XL[103X. Since the returned code is still linear, it is very likely that, besides
the words of [3XL[103X, more codewords of [3XC[103X are no longer in the new code.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := HammingCode( 4 );; WeightDistribution( C1 );[127X[104X
[4X[28X[ 1, 0, 0, 35, 105, 168, 280, 435, 435, 280, 168, 105, 35, 0, 0, 1 ][128X[104X
[4X[25Xgap>[125X [27XL := Filtered( AsSSortedList(C1), i -> WeightCodeword(i) = 3 );;[127X[104X
[4X[25Xgap>[125X [27XC2 := ExpurgatedCode( C1, L );[127X[104X
[4X[28Xa linear [15,4,3..4]5..11 code, expurgated with 7 word(s)[128X[104X
[4X[25Xgap>[125X [27XWeightDistribution( C2 );[127X[104X
[4X[28X[ 1, 0, 0, 0, 14, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0 ] [128X[104X
[4X[32X[104X
[33X[0;0YThis function does not work on non-linear codes. For removing words from a
non-linear code, use [10XRemovedElementsCode[110X (see [2XRemovedElementsCode[102X ([14X6.1-7[114X)).
For expurgating a code of all words of odd weight, use `EvenWeightSubcode'
(see [2XEvenWeightSubcode[102X ([14X6.1-3[114X)).[133X
[1X6.1-6 AugmentedCode[101X
[29X[2XAugmentedCode[102X( [3XC[103X, [3XL[103X ) [32X function
[33X[0;0Y[10XAugmentedCode[110X returns [3XC[103X after augmenting. [3XC[103X must be a linear code, [3XL[103X must be
a list of codeword inputs. The generator matrix of the new code is a basis
for the codewords specified by [3XL[103X as well as the words that were already in
code [3XC[103X. Note that the new code in general will consist of more words than
only the codewords of [3XC[103X and the words [3XL[103X. The returned code is also a linear
code.[133X
[33X[0;0YThis command can also be called with the syntax [10XAugmentedCode(C)[110X. When
called without a list of codewords, [10XAugmentedCode[110X returns [3XC[103X after adding the
all-ones vector to the generator matrix. [3XC[103X must be a linear code. If the
all-ones vector was already in the code, nothing happens and a copy of the
argument is returned. If [3XC[103X is a binary code which does not contain the
all-ones vector, the complement of all codewords is added.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC31 := ReedMullerCode( 1, 3 );[127X[104X
[4X[28Xa linear [8,4,4]2 Reed-Muller (1,3) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC32 := AugmentedCode(C31,["00000011","00000101","00010001"]);[127X[104X
[4X[28Xa linear [8,7,1..2]1 code, augmented with 3 word(s)[128X[104X
[4X[25Xgap>[125X [27XC32 = ReedMullerCode( 2, 3 );[127X[104X
[4X[28Xtrue [128X[104X
[4X[25Xgap>[125X [27XC1 := CordaroWagnerCode(6);[127X[104X
[4X[28Xa linear [6,2,4]2..3 Cordaro-Wagner code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XCodeword( [0,0,1,1,1,1] ) in C1;[127X[104X
[4X[28Xtrue[128X[104X
[4X[25Xgap>[125X [27XC2 := AugmentedCode( C1 );[127X[104X
[4X[28Xa linear [6,3,1..2]2..3 code, augmented with 1 word(s)[128X[104X
[4X[25Xgap>[125X [27XCodeword( [1,1,0,0,0,0] ) in C2;[127X[104X
[4X[28Xtrue[128X[104X
[4X[32X[104X
[33X[0;0YThe function [10XAddedElementsCode[110X adds elements to the codewords instead of
adding them to the basis (see [2XAddedElementsCode[102X ([14X6.1-8[114X)).[133X
[1X6.1-7 RemovedElementsCode[101X
[29X[2XRemovedElementsCode[102X( [3XC[103X, [3XL[103X ) [32X function
[33X[0;0Y[10XRemovedElementsCode[110X returns code [3XC[103X after removing a list of codewords [3XL[103X from
its elements. [3XL[103X must be a list of codeword input. The result is an
unrestricted code.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := HammingCode( 4 );; WeightDistribution( C1 );[127X[104X
[4X[28X[ 1, 0, 0, 35, 105, 168, 280, 435, 435, 280, 168, 105, 35, 0, 0, 1 ][128X[104X
[4X[25Xgap>[125X [27XL := Filtered( AsSSortedList(C1), i -> WeightCodeword(i) = 3 );;[127X[104X
[4X[25Xgap>[125X [27XC2 := RemovedElementsCode( C1, L );[127X[104X
[4X[28Xa (15,2013,3..15)2..15 code with 35 word(s) removed[128X[104X
[4X[25Xgap>[125X [27XWeightDistribution( C2 );[127X[104X
[4X[28X[ 1, 0, 0, 0, 105, 168, 280, 435, 435, 280, 168, 105, 35, 0, 0, 1 ][128X[104X
[4X[25Xgap>[125X [27XMinimumDistance( C2 );[127X[104X
[4X[28X3 # C2 is not linear, so the minimum weight does not have to[128X[104X
[4X[28X # be equal to the minimum distance [128X[104X
[4X[32X[104X
[33X[0;0YAdding elements to a code is done by the function [10XAddedElementsCode[110X (see
[2XAddedElementsCode[102X ([14X6.1-8[114X)). To remove codewords from the base of a linear
code, use [10XExpurgatedCode[110X (see [2XExpurgatedCode[102X ([14X6.1-5[114X)).[133X
[1X6.1-8 AddedElementsCode[101X
[29X[2XAddedElementsCode[102X( [3XC[103X, [3XL[103X ) [32X function
[33X[0;0Y[10XAddedElementsCode[110X returns code [3XC[103X after adding a list of codewords [3XL[103X to its
elements. [3XL[103X must be a list of codeword input. The result is an unrestricted
code.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := NullCode( 6, GF(2) );[127X[104X
[4X[28Xa cyclic [6,0,6]6 nullcode over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 := AddedElementsCode( C1, [ "111111" ] );[127X[104X
[4X[28Xa (6,2,1..6)3 code with 1 word(s) added[128X[104X
[4X[25Xgap>[125X [27XIsCyclicCode( C2 );[127X[104X
[4X[28Xtrue[128X[104X
[4X[25Xgap>[125X [27XC3 := AddedElementsCode( C2, [ "101010", "010101" ] );[127X[104X
[4X[28Xa (6,4,1..6)2 code with 2 word(s) added[128X[104X
[4X[25Xgap>[125X [27XIsCyclicCode( C3 );[127X[104X
[4X[28Xtrue [128X[104X
[4X[32X[104X
[33X[0;0YTo remove elements from a code, use [10XRemovedElementsCode[110X (see
[2XRemovedElementsCode[102X ([14X6.1-7[114X)). To add elements to the base of a linear code,
use [10XAugmentedCode[110X (see [2XAugmentedCode[102X ([14X6.1-6[114X)).[133X
[1X6.1-9 ShortenedCode[101X
[29X[2XShortenedCode[102X( [3XC[103X[, [3XL[103X] ) [32X function
[33X[0;0Y[10XShortenedCode( C )[110X returns the code [3XC[103X shortened by taking a cross section.
If [3XC[103X is a linear code, this is done by removing all codewords that start
with a non-zero entry, after which the first column is cut off. If [3XC[103X was a
[22X[n,k,d][122X code, the shortened code generally is a [22X[n-1,k-1,d][122X code. It is
possible that the dimension remains the same; it is also possible that the
minimum distance increases.[133X
[33X[0;0YIf [3XC[103X is a non-linear code, [10XShortenedCode[110X first checks which finite field
element occurs most often in the first column of the codewords. The
codewords not starting with this element are removed from the code, after
which the first column is cut off. The resulting shortened code has at least
the same minimum distance as [3XC[103X.[133X
[33X[0;0YThis command can also be called using the syntax [10XShortenedCode(C,L)[110X. When
called in this format, [10XShortenedCode[110X repeats the shortening process on each
of the columns specified by [3XL[103X. [3XL[103X therefore is a list of integers. The column
numbers in [3XL[103X are the numbers as they are before the shortening process. If [3XL[103X
has [22Xl[122X entries, the returned code has a word length of [22Xl[122X positions shorter
than [3XC[103X.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := HammingCode( 4 );[127X[104X
[4X[28Xa linear [15,11,3]1 Hamming (4,2) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 := ShortenedCode( C1 );[127X[104X
[4X[28Xa linear [14,10,3]2 shortened code[128X[104X
[4X[25Xgap>[125X [27XC3 := ElementsCode( ["1000", "1101", "0011" ], GF(2) );[127X[104X
[4X[28Xa (4,3,1..4)2 user defined unrestricted code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XMinimumDistance( C3 );[127X[104X
[4X[28X2[128X[104X
[4X[25Xgap>[125X [27XC4 := ShortenedCode( C3 );[127X[104X
[4X[28Xa (3,2,2..3)1..2 shortened code[128X[104X
[4X[25Xgap>[125X [27XAsSSortedList( C4 );[127X[104X
[4X[28X[ [ 0 0 0 ], [ 1 0 1 ] ][128X[104X
[4X[25Xgap>[125X [27XC5 := HammingCode( 5, GF(2) );[127X[104X
[4X[28Xa linear [31,26,3]1 Hamming (5,2) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC6 := ShortenedCode( C5, [ 1, 2, 3 ] );[127X[104X
[4X[28Xa linear [28,23,3]2 shortened code[128X[104X
[4X[25Xgap>[125X [27XOptimalityLinearCode( C6 );[127X[104X
[4X[28X0[128X[104X
[4X[32X[104X
[33X[0;0YThe function [10XLengthenedCode[110X lengthens the code again (only for linear
codes), see [2XLengthenedCode[102X ([14X6.1-10[114X). In general, this is not exactly the
inverse function.[133X
[1X6.1-10 LengthenedCode[101X
[29X[2XLengthenedCode[102X( [3XC[103X[, [3Xi[103X] ) [32X function
[33X[0;0Y[10XLengthenedCode( C )[110X returns the code [3XC[103X lengthened. [3XC[103X must be a linear code.
First, the all-ones vector is added to the generator matrix (see
[2XAugmentedCode[102X ([14X6.1-6[114X)). If the all-ones vector was already a codeword,
nothing happens to the code. Then, the code is extended [3Xi[103X times (see
[2XExtendedCode[102X ([14X6.1-1[114X)). [3Xi[103X is equal to [22X1[122X by default. If [3XC[103X was an [22X[n,k][122X code,
the new code generally is a [22X[n+i,k+1][122X code.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := CordaroWagnerCode( 5 );[127X[104X
[4X[28Xa linear [5,2,3]2 Cordaro-Wagner code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 := LengthenedCode( C1 );[127X[104X
[4X[28Xa linear [6,3,2]2..3 code, lengthened with 1 column(s) [128X[104X
[4X[32X[104X
[33X[0;0Y[10XShortenedCode[110X' shortens the code, see [2XShortenedCode[102X ([14X6.1-9[114X). In general,
this is not exactly the inverse function.[133X
[1X6.1-11 SubCode[101X
[29X[2XSubCode[102X( [3XC[103X[, [3Xs[103X] ) [32X function
[33X[0;0YThis function [10XSubCode[110X returns a subcode of [3XC[103X by taking the first [22Xk - s[122X rows
of the generator matrix of [3XC[103X, where [22Xk[122X is the dimension of [3XC[103X. The interger [3Xs[103X
may be omitted and in this case it is assumed as 1.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC := BCHCode(31,11);[127X[104X
[4X[28Xa cyclic [31,11,11]7..11 BCH code, delta=11, b=1 over GF(2)[128X[104X
[4X[25Xgap>[125X [27XS1:= SubCode(C);[127X[104X
[4X[28Xa linear [31,10,11]7..13 subcode[128X[104X
[4X[25Xgap>[125X [27XWeightDistribution(S1);[127X[104X
[4X[28X[ 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 120, 190, 0, 0, 272, 255, 0, 0, 120, 66,[128X[104X
[4X[28X 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ][128X[104X
[4X[25Xgap>[125X [27XS2:= SubCode(C, 8);[127X[104X
[4X[28Xa linear [31,3,11]14..20 subcode[128X[104X
[4X[25Xgap>[125X [27XHistory(S2);[127X[104X
[4X[28X[ "a linear [31,3,11]14..20 subcode of",[128X[104X
[4X[28X "a cyclic [31,11,11]7..11 BCH code, delta=11, b=1 over GF(2)" ][128X[104X
[4X[25Xgap>[125X [27XWeightDistribution(S2);[127X[104X
[4X[28X[ 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0,[128X[104X
[4X[28X 0, 0, 0, 0, 0, 0, 0 ][128X[104X
[4X[32X[104X
[1X6.1-12 ResidueCode[101X
[29X[2XResidueCode[102X( [3XC[103X[, [3Xc[103X] ) [32X function
[33X[0;0YThe function [10XResidueCode[110X takes a codeword [3Xc[103X of [3XC[103X (if [3Xc[103X is omitted, a
codeword of minimal weight is used). It removes this word and all its linear
combinations from the code and then punctures the code in the coordinates
where [3Xc[103X is unequal to zero. The resulting code is an [22X[n-w, k-1, d-⌊
w*(q-1)/q ⌋ ][122X code. [3XC[103X must be a linear code and [3Xc[103X must be non-zero. If [3Xc[103X is
not in [3X[103X then no change is made to [3XC[103X.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := BCHCode( 15, 7 );[127X[104X
[4X[28Xa cyclic [15,5,7]5 BCH code, delta=7, b=1 over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 := ResidueCode( C1 );[127X[104X
[4X[28Xa linear [8,4,4]2 residue code[128X[104X
[4X[25Xgap>[125X [27Xc := Codeword( [ 0,0,0,1,0,0,1,1,0,1,0,1,1,1,1 ], C1);;[127X[104X
[4X[25Xgap>[125X [27XC3 := ResidueCode( C1, c );[127X[104X
[4X[28Xa linear [7,4,3]1 residue code [128X[104X
[4X[32X[104X
[1X6.1-13 ConstructionBCode[101X
[29X[2XConstructionBCode[102X( [3XC[103X ) [32X function
[33X[0;0YThe function [10XConstructionBCode[110X takes a binary linear code [3XC[103X and calculates
the minimum distance of the dual of [3XC[103X (see [2XDualCode[102X ([14X6.1-14[114X)). It then
removes the columns of the parity check matrix of [3XC[103X where a codeword of the
dual code of minimal weight has coordinates unequal to zero. The resulting
matrix is a parity check matrix for an [22X[n-dd, k-dd+1, ≥ d][122X code, where [22Xdd[122X is
the minimum distance of the dual of [3XC[103X.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := ReedMullerCode( 2, 5 );[127X[104X
[4X[28Xa linear [32,16,8]6 Reed-Muller (2,5) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 := ConstructionBCode( C1 );[127X[104X
[4X[28Xa linear [24,9,8]5..10 Construction B (8 coordinates)[128X[104X
[4X[25Xgap>[125X [27XBoundsMinimumDistance( 24, 9, GF(2) );[127X[104X
[4X[28Xrec( n := 24, k := 9, q := 2, references := rec( ), [128X[104X
[4X[28X construction := [ [ Operation "UUVCode" ], [128X[104X
[4X[28X [ [ [ Operation "UUVCode" ], [ [ [ Operation "DualCode" ], [128X[104X
[4X[28X [ [ [ Operation "RepetitionCode" ], [ 6, 2 ] ] ] ], [128X[104X
[4X[28X [ [ Operation "CordaroWagnerCode" ], [ 6 ] ] ] ], [128X[104X
[4X[28X [ [ Operation "CordaroWagnerCode" ], [ 12 ] ] ] ], lowerBound := 8, [128X[104X
[4X[28X lowerBoundExplanation := [ "Lb(24,9)=8, u u+v construction of C1 and C2:", [128X[104X
[4X[28X "Lb(12,7)=4, u u+v construction of C1 and C2:", [128X[104X
[4X[28X "Lb(6,5)=2, dual of the repetition code", [128X[104X
[4X[28X "Lb(6,2)=4, Cordaro-Wagner code", "Lb(12,2)=8, Cordaro-Wagner code" ], [128X[104X
[4X[28X upperBound := 8, [128X[104X
[4X[28X upperBoundExplanation := [ "Ub(24,9)=8, otherwise construction B would [128X[104X
[4X[28X contradict:", "Ub(18,4)=8, Griesmer bound" ] )[128X[104X
[4X[28X# so C2 is optimal[128X[104X
[4X[32X[104X
[1X6.1-14 DualCode[101X
[29X[2XDualCode[102X( [3XC[103X ) [32X function
[33X[0;0Y[10XDualCode[110X returns the dual code of [3XC[103X. The dual code consists of all codewords
that are orthogonal to the codewords of [3XC[103X. If [3XC[103X is a linear code with
generator matrix [22XG[122X, the dual code has parity check matrix [22XG[122X (or if [3XC[103X has
parity check matrix [22XH[122X, the dual code has generator matrix [22XH[122X). So if [3XC[103X is a
linear [22X[n, k][122X code, the dual code of [3XC[103X is a linear [22X[n, n-k][122X code. If [3XC[103X is a
cyclic code with generator polynomial [22Xg(x)[122X, the dual code has the reciprocal
polynomial of [22Xg(x)[122X as check polynomial.[133X
[33X[0;0YThe dual code is always a linear code, even if [3XC[103X is non-linear.[133X
[33X[0;0YIf a code [3XC[103X is equal to its dual code, it is called [13Xself-dual[113X.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XR := ReedMullerCode( 1, 3 );[127X[104X
[4X[28Xa linear [8,4,4]2 Reed-Muller (1,3) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XRD := DualCode( R );[127X[104X
[4X[28Xa linear [8,4,4]2 Reed-Muller (1,3) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XR = RD;[127X[104X
[4X[28Xtrue[128X[104X
[4X[25Xgap>[125X [27XN := WholeSpaceCode( 7, GF(4) );[127X[104X
[4X[28Xa cyclic [7,7,1]0 whole space code over GF(4)[128X[104X
[4X[25Xgap>[125X [27XDualCode( N ) = NullCode( 7, GF(4) );[127X[104X
[4X[28Xtrue [128X[104X
[4X[32X[104X
[1X6.1-15 ConversionFieldCode[101X
[29X[2XConversionFieldCode[102X( [3XC[103X ) [32X function
[33X[0;0Y[10XConversionFieldCode[110X returns the code obtained from [3XC[103X after converting its
field. If the field of [3XC[103X is [22XGF(q^m)[122X, the returned code has field [22XGF(q)[122X. Each
symbol of every codeword is replaced by a concatenation of [22Xm[122X symbols from
[22XGF(q)[122X. If [3XC[103X is an [22X(n, M, d_1)[122X code, the returned code is a [22X(n⋅ m, M, d_2)[122X
code, where [22Xd_2 > d_1[122X.[133X
[33X[0;0YSee also [2XHorizontalConversionFieldMat[102X ([14X7.3-10[114X).[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XR := RepetitionCode( 4, GF(4) );[127X[104X
[4X[28Xa cyclic [4,1,4]3 repetition code over GF(4)[128X[104X
[4X[25Xgap>[125X [27XR2 := ConversionFieldCode( R );[127X[104X
[4X[28Xa linear [8,2,4]3..4 code, converted to basefield GF(2)[128X[104X
[4X[25Xgap>[125X [27XSize( R ) = Size( R2 );[127X[104X
[4X[28Xtrue[128X[104X
[4X[25Xgap>[125X [27XGeneratorMat( R );[127X[104X
[4X[28X[ [ Z(2)^0, Z(2)^0, Z(2)^0, Z(2)^0 ] ][128X[104X
[4X[25Xgap>[125X [27XGeneratorMat( R2 );[127X[104X
[4X[28X[ [ Z(2)^0, 0*Z(2), Z(2)^0, 0*Z(2), Z(2)^0, 0*Z(2), Z(2)^0, 0*Z(2) ],[128X[104X
[4X[28X [ 0*Z(2), Z(2)^0, 0*Z(2), Z(2)^0, 0*Z(2), Z(2)^0, 0*Z(2), Z(2)^0 ] ] [128X[104X
[4X[32X[104X
[1X6.1-16 TraceCode[101X
[29X[2XTraceCode[102X( [3XC[103X ) [32X function
[33X[0;0YInput: [3XC[103X is a linear code defined over an extension [22XE[122X of [3XF[103X ([3XF[103X is the ``base
field'')[133X
[33X[0;0YOutput: The linear code generated by [22XTr_E/F(c)[122X, for all [22Xc ∈ C[122X.[133X
[33X[0;0Y[10XTraceCode[110X returns the image of the code [3XC[103X under the trace map. If the field
of [3XC[103X is [22XGF(q^m)[122X, the returned code has field [22XGF(q)[122X.[133X
[33X[0;0YVery slow. It does not seem to be easy to related the parameters of the
trace code to the original except in the ``Galois closed'' case.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC:=RandomLinearCode(10,4,GF(4)); MinimumDistance(C);[127X[104X
[4X[28Xa [10,4,?] randomly generated code over GF(4)[128X[104X
[4X[28X5[128X[104X
[4X[25Xgap>[125X [27XtrC:=TraceCode(C,GF(2)); MinimumDistance(trC);[127X[104X
[4X[28Xa linear [10,7,1]1..3 user defined unrestricted code over GF(2)[128X[104X
[4X[28X1[128X[104X
[4X[28X[128X[104X
[4X[32X[104X
[1X6.1-17 CosetCode[101X
[29X[2XCosetCode[102X( [3XC[103X, [3Xw[103X ) [32X function
[33X[0;0Y[10XCosetCode[110X returns the coset of a code [3XC[103X with respect to word [3Xw[103X. [3Xw[103X must be of
the codeword type. Then, [3Xw[103X is added to each codeword of [3XC[103X, yielding the
elements of the new code. If [3XC[103X is linear and [3Xw[103X is an element of [3XC[103X, the new
code is equal to [3XC[103X, otherwise the new code is an unrestricted code.[133X
[33X[0;0YGenerating a coset is also possible by simply adding the word [3Xw[103X to [3XC[103X. See
[14X4.2[114X.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XH := HammingCode(3, GF(2));[127X[104X
[4X[28Xa linear [7,4,3]1 Hamming (3,2) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27Xc := Codeword("1011011");; c in H;[127X[104X
[4X[28Xfalse[128X[104X
[4X[25Xgap>[125X [27XC := CosetCode(H, c);[127X[104X
[4X[28Xa (7,16,3)1 coset code[128X[104X
[4X[25Xgap>[125X [27XList(AsSSortedList(C), el-> Syndrome(H, el));[127X[104X
[4X[28X[ [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ],[128X[104X
[4X[28X [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ],[128X[104X
[4X[28X [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ], [ 1 1 1 ] ][128X[104X
[4X[28X# All elements of the coset have the same syndrome in H [128X[104X
[4X[32X[104X
[1X6.1-18 ConstantWeightSubcode[101X
[29X[2XConstantWeightSubcode[102X( [3XC[103X, [3Xw[103X ) [32X function
[33X[0;0Y[10XConstantWeightSubcode[110X returns the subcode of [3XC[103X that only has codewords of
weight [3Xw[103X. The resulting code is a non-linear code, because it does not
contain the all-zero vector.[133X
[33X[0;0YThis command also can be called with the syntax [10XConstantWeightSubcode(C)[110X In
this format, [10XConstantWeightSubcode[110X returns the subcode of [3XC[103X consisting of
all minimum weight codewords of [3XC[103X.[133X
[33X[0;0Y[10XConstantWeightSubcode[110X first checks if Leon's binary [10Xwtdist[110X exists on your
computer (in the default directory). If it does, then this program is
called. Otherwise, the constant weight subcode is computed using a GAP
program which checks each codeword in [3XC[103X to see if it is of the desired
weight.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XN := NordstromRobinsonCode();; WeightDistribution(N);[127X[104X
[4X[28X[ 1, 0, 0, 0, 0, 0, 112, 0, 30, 0, 112, 0, 0, 0, 0, 0, 1 ][128X[104X
[4X[25Xgap>[125X [27XC := ConstantWeightSubcode(N, 8);[127X[104X
[4X[28Xa (16,30,6..16)5..8 code with codewords of weight 8[128X[104X
[4X[25Xgap>[125X [27XWeightDistribution(C);[127X[104X
[4X[28X[ 0, 0, 0, 0, 0, 0, 0, 0, 30, 0, 0, 0, 0, 0, 0, 0, 0 ] [128X[104X
[4X[25Xgap>[125X [27Xeg := ExtendedTernaryGolayCode();; WeightDistribution(eg);[127X[104X
[4X[28X[ 1, 0, 0, 0, 0, 0, 264, 0, 0, 440, 0, 0, 24 ][128X[104X
[4X[25Xgap>[125X [27XC := ConstantWeightSubcode(eg);[127X[104X
[4X[28Xa (12,264,6..12)3..6 code with codewords of weight 6[128X[104X
[4X[25Xgap>[125X [27XWeightDistribution(C);[127X[104X
[4X[28X[ 0, 0, 0, 0, 0, 0, 264, 0, 0, 0, 0, 0, 0 ] [128X[104X
[4X[32X[104X
[1X6.1-19 StandardFormCode[101X
[29X[2XStandardFormCode[102X( [3XC[103X ) [32X function
[33X[0;0Y[10XStandardFormCode[110X returns [3XC[103X after putting it in standard form. If [3XC[103X is a
non-linear code, this means the elements are organized using lexicographical
order. This means they form a legal GAP `Set'.[133X
[33X[0;0YIf [3XC[103X is a linear code, the generator matrix and parity check matrix are put
in standard form. The generator matrix then has an identity matrix in its
left part, the parity check matrix has an identity matrix in its right part.
Although [5XGUAVA[105X always puts both matrices in a standard form using [10XBaseMat[110X,
this never alters the code. [10XStandardFormCode[110X even applies column
permutations if unavoidable, and thereby changes the code. The column
permutations are recorded in the construction history of the new code (see
[2XDisplay[102X ([14X4.6-3[114X)). [3XC[103X and the new code are of course equivalent.[133X
[33X[0;0YIf [3XC[103X is a cyclic code, its generator matrix cannot be put in the usual upper
triangular form, because then it would be inconsistent with the generator
polynomial. The reason is that generating the elements from the generator
matrix would result in a different order than generating the elements from
the generator polynomial. This is an unwanted effect, and therefore
[10XStandardFormCode[110X just returns a copy of [3XC[103X for cyclic codes.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XG := GeneratorMatCode( Z(2) * [ [0,1,1,0], [0,1,0,1], [0,0,1,1] ], [127X[104X
[4X[28X "random form code", GF(2) );[128X[104X
[4X[28Xa linear [4,2,1..2]1..2 random form code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XCodeword( GeneratorMat( G ) );[127X[104X
[4X[28X[ [ 0 1 0 1 ], [ 0 0 1 1 ] ][128X[104X
[4X[25Xgap>[125X [27XCodeword( GeneratorMat( StandardFormCode( G ) ) );[127X[104X
[4X[28X[ [ 1 0 0 1 ], [ 0 1 0 1 ] ] [128X[104X
[4X[32X[104X
[1X6.1-20 PiecewiseConstantCode[101X
[29X[2XPiecewiseConstantCode[102X( [3Xpart[103X, [3Xwts[103X[, [3XF[103X] ) [32X function
[33X[0;0Y[10XPiecewiseConstantCode[110X returns a code with length [22Xn = ∑ n_i[122X, where [3Xpart[103X=[22X[
n_1, dots, n_k ][122X. [3Xwts[103X is a list of [3Xconstraints[103X [22Xw=(w_1,...,w_k)[122X, each of
length [22Xk[122X, where [22X0 ≤ w_i ≤ n_i[122X. The default field is [22XGF(2)[122X.[133X
[33X[0;0YA constraint is a list of integers, and a word [22Xc = ( c_1, dots, c_k )[122X
(according to [3Xpart[103X, i.e., each [22Xc_i[122X is a subword of length [22Xn_i[122X) is in the
resulting code if and only if, for some constraint [22Xw ∈[122X [3Xwts[103X, [22X|c_i| = w_i[122X for
all [22X1 ≤ i ≤ k[122X, where [22X| ...|[122X denotes the Hamming weight.[133X
[33X[0;0YAn example might make things clearer:[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XPiecewiseConstantCode( [ 2, 3 ],[127X[104X
[4X[28X [ [ 0, 0 ], [ 0, 3 ], [ 1, 0 ], [ 2, 2 ] ],GF(2) );[128X[104X
[4X[28Xthe C code programs are compiled, so using Leon's binary....[128X[104X
[4X[28Xthe C code programs are compiled, so using Leon's binary....[128X[104X
[4X[28Xthe C code programs are compiled, so using Leon's binary....[128X[104X
[4X[28Xthe C code programs are compiled, so using Leon's binary....[128X[104X
[4X[28Xa (5,7,1..5)1..5 piecewise constant code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XAsSSortedList(last);[127X[104X
[4X[28X[ [ 0 0 0 0 0 ], [ 0 0 1 1 1 ], [ 0 1 0 0 0 ], [ 1 0 0 0 0 ], [128X[104X
[4X[28X [ 1 1 0 1 1 ], [ 1 1 1 0 1 ], [ 1 1 1 1 0 ] ][128X[104X
[4X[28Xgap>[128X[104X
[4X[28X[128X[104X
[4X[32X[104X
[33X[0;0YThe first constraint is satisfied by codeword 1, the second by codeword 2,
the third by codewords 3 and 4, and the fourth by codewords 5, 6 and 7.[133X
[1X6.2 [33X[0;0YFunctions that Generate a New Code from Two or More Given Codes[133X[101X
[1X6.2-1 DirectSumCode[101X
[29X[2XDirectSumCode[102X( [3XC1[103X, [3XC2[103X ) [32X function
[33X[0;0Y[10XDirectSumCode[110X returns the direct sum of codes [3XC1[103X and [3XC2[103X. The direct sum code
consists of every codeword of [3XC1[103X concatenated by every codeword of [3XC2[103X.
Therefore, if [3XCi[103X was a [22X(n_i,M_i,d_i)[122X code, the result is a
[22X(n_1+n_2,M_1*M_2,min(d_1,d_2))[122X code.[133X
[33X[0;0YIf both [3XC1[103X and [3XC2[103X are linear codes, the result is also a linear code. If one
of them is non-linear, the direct sum is non-linear too. In general, a
direct sum code is not cyclic.[133X
[33X[0;0YPerforming a direct sum can also be done by adding two codes (see Section
[14X4.2[114X). Another often used method is the `u, u+v'-construction, described in
[2XUUVCode[102X ([14X6.2-2[114X).[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := ElementsCode( [ [1,0], [4,5] ], GF(7) );;[127X[104X
[4X[25Xgap>[125X [27XC2 := ElementsCode( [ [0,0,0], [3,3,3] ], GF(7) );;[127X[104X
[4X[25Xgap>[125X [27XD := DirectSumCode(C1, C2);;[127X[104X
[4X[25Xgap>[125X [27XAsSSortedList(D);[127X[104X
[4X[28X[ [ 1 0 0 0 0 ], [ 1 0 3 3 3 ], [ 4 5 0 0 0 ], [ 4 5 3 3 3 ] ][128X[104X
[4X[25Xgap>[125X [27XD = C1 + C2; # addition = direct sum[127X[104X
[4X[28Xtrue [128X[104X
[4X[32X[104X
[1X6.2-2 UUVCode[101X
[29X[2XUUVCode[102X( [3XC1[103X, [3XC2[103X ) [32X function
[33X[0;0Y[10XUUVCode[110X returns the so-called [22X(u|u+v)[122X construction applied to [3XC1[103X and [3XC2[103X. The
resulting code consists of every codeword [22Xu[122X of [3XC1[103X concatenated by the sum of
[22Xu[122X and every codeword [22Xv[122X of [3XC2[103X. If [3XC1[103X and [3XC2[103X have different word lengths,
sufficient zeros are added to the shorter code to make this sum possible. If
[3XCi[103X is a [22X(n_i,M_i,d_i)[122X code, the result is an [22X(n_1+max(n_1,n_2),M_1⋅
M_2,min(2⋅ d_1,d_2))[122X code.[133X
[33X[0;0YIf both [3XC1[103X and [3XC2[103X are linear codes, the result is also a linear code. If one
of them is non-linear, the UUV sum is non-linear too. In general, a UUV sum
code is not cyclic.[133X
[33X[0;0YThe function [10XDirectSumCode[110X returns another sum of codes (see [2XDirectSumCode[102X
([14X6.2-1[114X)).[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := EvenWeightSubcode(WholeSpaceCode(4, GF(2)));[127X[104X
[4X[28Xa cyclic [4,3,2]1 even weight subcode[128X[104X
[4X[25Xgap>[125X [27XC2 := RepetitionCode(4, GF(2));[127X[104X
[4X[28Xa cyclic [4,1,4]2 repetition code over GF(2)[128X[104X
[4X[25Xgap>[125X [27XR := UUVCode(C1, C2);[127X[104X
[4X[28Xa linear [8,4,4]2 U U+V construction code[128X[104X
[4X[25Xgap>[125X [27XR = ReedMullerCode(1,3);[127X[104X
[4X[28Xtrue [128X[104X
[4X[32X[104X
[1X6.2-3 DirectProductCode[101X
[29X[2XDirectProductCode[102X( [3XC1[103X, [3XC2[103X ) [32X function
[33X[0;0Y[10XDirectProductCode[110X returns the direct product of codes [3XC1[103X and [3XC2[103X. Both must
be linear codes. Suppose [3XCi[103X has generator matrix [22XG_i[122X. The direct product of
[3XC1[103X and [3XC2[103X then has the Kronecker product of [22XG_1[122X and [22XG_2[122X as the generator
matrix (see the GAP command [10XKroneckerProduct[110X).[133X
[33X[0;0YIf [3XCi[103X is a [22X[n_i, k_i, d_i][122X code, the direct product then is an [22X[n_1⋅
n_2,k_1⋅ k_2,d_1⋅ d_2][122X code.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XL1 := LexiCode(10, 4, GF(2));[127X[104X
[4X[28Xa linear [10,5,4]2..4 lexicode over GF(2)[128X[104X
[4X[25Xgap>[125X [27XL2 := LexiCode(8, 3, GF(2));[127X[104X
[4X[28Xa linear [8,4,3]2..3 lexicode over GF(2)[128X[104X
[4X[25Xgap>[125X [27XD := DirectProductCode(L1, L2);[127X[104X
[4X[28Xa linear [80,20,12]20..45 direct product code [128X[104X
[4X[32X[104X
[1X6.2-4 IntersectionCode[101X
[29X[2XIntersectionCode[102X( [3XC1[103X, [3XC2[103X ) [32X function
[33X[0;0Y[10XIntersectionCode[110X returns the intersection of codes [3XC1[103X and [3XC2[103X. This code
consists of all codewords that are both in [3XC1[103X and [3XC2[103X. If both codes are
linear, the result is also linear. If both are cyclic, the result is also
cyclic.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC := CyclicCodes(7, GF(2));[127X[104X
[4X[28X[ a cyclic [7,7,1]0 enumerated code over GF(2),[128X[104X
[4X[28X a cyclic [7,6,1..2]1 enumerated code over GF(2),[128X[104X
[4X[28X a cyclic [7,3,1..4]2..3 enumerated code over GF(2),[128X[104X
[4X[28X a cyclic [7,0,7]7 enumerated code over GF(2),[128X[104X
[4X[28X a cyclic [7,3,1..4]2..3 enumerated code over GF(2),[128X[104X
[4X[28X a cyclic [7,4,1..3]1 enumerated code over GF(2),[128X[104X
[4X[28X a cyclic [7,1,7]3 enumerated code over GF(2),[128X[104X
[4X[28X a cyclic [7,4,1..3]1 enumerated code over GF(2) ][128X[104X
[4X[25Xgap>[125X [27XIntersectionCode(C[6], C[8]) = C[7];[127X[104X
[4X[28Xtrue [128X[104X
[4X[32X[104X
[33X[0;0YThe [13Xhull[113X of a linear code is the intersection of the code with its dual
code. In other words, the hull of [22XC[122X is [10XIntersectionCode(C, DualCode(C))[110X.[133X
[1X6.2-5 UnionCode[101X
[29X[2XUnionCode[102X( [3XC1[103X, [3XC2[103X ) [32X function
[33X[0;0Y[10XUnionCode[110X returns the union of codes [3XC1[103X and [3XC2[103X. This code consists of the
union of all codewords of [3XC1[103X and [3XC2[103X and all linear combinations. Therefore
this function works only for linear codes. The function [10XAddedElementsCode[110X
can be used for non-linear codes, or if the resulting code should not
include linear combinations. See [2XAddedElementsCode[102X ([14X6.1-8[114X). If both
arguments are cyclic, the result is also cyclic.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XG := GeneratorMatCode([[1,0,1],[0,1,1]]*Z(2)^0, GF(2));[127X[104X
[4X[28Xa linear [3,2,1..2]1 code defined by generator matrix over GF(2)[128X[104X
[4X[25Xgap>[125X [27XH := GeneratorMatCode([[1,1,1]]*Z(2)^0, GF(2));[127X[104X
[4X[28Xa linear [3,1,3]1 code defined by generator matrix over GF(2)[128X[104X
[4X[25Xgap>[125X [27XU := UnionCode(G, H);[127X[104X
[4X[28Xa linear [3,3,1]0 union code[128X[104X
[4X[25Xgap>[125X [27Xc := Codeword("010");; c in G;[127X[104X
[4X[28Xfalse[128X[104X
[4X[25Xgap>[125X [27Xc in H;[127X[104X
[4X[28Xfalse[128X[104X
[4X[25Xgap>[125X [27Xc in U;[127X[104X
[4X[28Xtrue [128X[104X
[4X[32X[104X
[1X6.2-6 ExtendedDirectSumCode[101X
[29X[2XExtendedDirectSumCode[102X( [3XL[103X, [3XB[103X, [3Xm[103X ) [32X function
[33X[0;0YThe extended direct sum construction is described in section V of Graham and
Sloane [GS85]. The resulting code consists of [3Xm[103X copies of [3XL[103X, extended by
repeating the codewords of [3XB[103X [3Xm[103X times.[133X
[33X[0;0YSuppose [3XL[103X is an [22X[n_L, k_L]r_L[122X code, and [3XB[103X is an [22X[n_L, k_B]r_B[122X code
(non-linear codes are also permitted). The length of [3XB[103X must be equal to the
length of [3XL[103X. The length of the new code is [22Xn = m n_L[122X, the dimension (in the
case of linear codes) is [22Xk ≤ m k_L + k_B[122X, and the covering radius is [22Xr ≤ ⌊ m
Ψ( L, B ) ⌋[122X, with[133X
[33X[1;6Y[24X[33X[0;0Y\Psi( L, B ) = \max_{u \in F_2^{n_L}} \frac{1}{2^{k_B}} \sum_{v \in B}
{\rm d}( L, v + u ).[133X [124X[133X
[33X[0;0YHowever, this computation will not be executed, because it may be too time
consuming for large codes.[133X
[33X[0;0YIf [22XL ⊆ B[122X, and [22XL[122X and [22XB[122X are linear codes, the last copy of [3XL[103X is omitted. In
this case the dimension is [22Xk = m k_L + (k_B - k_L)[122X.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27Xc := HammingCode( 3, GF(2) );[127X[104X
[4X[28Xa linear [7,4,3]1 Hamming (3,2) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27Xd := WholeSpaceCode( 7, GF(2) );[127X[104X
[4X[28Xa cyclic [7,7,1]0 whole space code over GF(2)[128X[104X
[4X[25Xgap>[125X [27Xe := ExtendedDirectSumCode( c, d, 3 );[127X[104X
[4X[28Xa linear [21,15,1..3]2 3-fold extended direct sum code[128X[104X
[4X[32X[104X
[1X6.2-7 AmalgamatedDirectSumCode[101X
[29X[2XAmalgamatedDirectSumCode[102X( [3Xc1[103X, [3Xc2[103X[, [3Xcheck[103X] ) [32X function
[33X[0;0Y[10XAmalgamatedDirectSumCode[110X returns the amalgamated direct sum of the codes [3Xc1[103X
and [3Xc2[103X. The amalgamated direct sum code consists of all codewords of the
form [22X(u | 0 | v)[122X if [22X(u | 0) ∈ c_1[122X and [22X(0 | v) ∈ c_2[122X and all codewords of the
form [22X(u | 1 | v)[122X if [22X(u | 1) ∈ c_1[122X and [22X(1 | v) ∈ c_2[122X. The result is a code
with length [22Xn = n_1 + n_2 - 1[122X and size [22XM ≤ M_1 ⋅ M_2 / 2[122X.[133X
[33X[0;0YIf both codes are linear, they will first be standardized, with information
symbols in the last and first coordinates of the first and second code,
respectively.[133X
[33X[0;0YIf [3Xc1[103X is a normal code (see [2XIsNormalCode[102X ([14X7.4-5[114X)) with the last coordinate
acceptable (see [2XIsCoordinateAcceptable[102X ([14X7.4-3[114X)), and [3Xc2[103X is a normal code
with the first coordinate acceptable, then the covering radius of the new
code is [22Xr ≤ r_1 + r_2[122X. However, checking whether a code is normal or not is
a lot of work, and almost all codes seem to be normal. Therefore, an option
[3Xcheck[103X can be supplied. If [3Xcheck[103X is true, then the codes will be checked for
normality. If [3Xcheck[103X is false or omitted, then the codes will not be checked.
In this case it is assumed that they are normal. Acceptability of the last
and first coordinate of the first and second code, respectively, is in the
last case also assumed to be done by the user.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27Xc := HammingCode( 3, GF(2) );[127X[104X
[4X[28Xa linear [7,4,3]1 Hamming (3,2) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27Xd := ReedMullerCode( 1, 4 );[127X[104X
[4X[28Xa linear [16,5,8]6 Reed-Muller (1,4) code over GF(2)[128X[104X
[4X[25Xgap>[125X [27Xe := DirectSumCode( c, d );[127X[104X
[4X[28Xa linear [23,9,3]7 direct sum code[128X[104X
[4X[25Xgap>[125X [27Xf := AmalgamatedDirectSumCode( c, d );;[127X[104X
[4X[25Xgap>[125X [27XMinimumDistance( f );;[127X[104X
[4X[25Xgap>[125X [27XCoveringRadius( f );; [127X[104X
[4X[25Xgap>[125X [27Xf;[127X[104X
[4X[28Xa linear [22,8,3]7 amalgamated direct sum code[128X[104X
[4X[32X[104X
[1X6.2-8 BlockwiseDirectSumCode[101X
[29X[2XBlockwiseDirectSumCode[102X( [3XC1[103X, [3XL1[103X, [3XC2[103X, [3XL2[103X ) [32X function
[33X[0;0Y[10XBlockwiseDirectSumCode[110X returns a subcode of the direct sum of [3XC1[103X and [3XC2[103X. The
fields of [3XC1[103X and [3XC2[103X must be same. The lists [3XL1[103X and [3XL2[103X are two equally long
with elements from the ambient vector spaces of [3XC1[103X and [3XC2[103X, respectively, [13Xor[113X
[3XL1[103X and [3XL2[103X are two equally long lists containing codes. The union of the
codes in [3XL1[103X and [3XL2[103X must be [3XC1[103X and [3XC2[103X, respectively.[133X
[33X[0;0YIn the first case, the blockwise direct sum code is defined as[133X
[33X[1;6Y[24X[33X[0;0Ybds = \bigcup_{1 \leq i \leq \ell} ( C_1 + (L_1)_i ) \oplus ( C_2 +
(L_2)_i ),[133X [124X[133X
[33X[0;0Ywhere [22Xℓ[122X is the length of [3XL1[103X and [3XL2[103X, and [22X⊕[122X is the direct sum.[133X
[33X[0;0YIn the second case, it is defined as[133X
[33X[1;6Y[24X[33X[0;0Ybds = \bigcup_{1 \leq i \leq \ell} ( (L_1)_i \oplus (L_2)_i ).[133X [124X[133X
[33X[0;0YThe length of the new code is [22Xn = n_1 + n_2[122X.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := HammingCode( 3, GF(2) );;[127X[104X
[4X[25Xgap>[125X [27XC2 := EvenWeightSubcode( WholeSpaceCode( 6, GF(2) ) );;[127X[104X
[4X[25Xgap>[125X [27XBlockwiseDirectSumCode( C1, [[ 0,0,0,0,0,0,0 ],[ 1,0,1,0,1,0,0 ]],[127X[104X
[4X[25X>[125X [27XC2, [[ 0,0,0,0,0,0 ],[ 1,0,1,0,1,0 ]] );[127X[104X
[4X[28Xa (13,1024,1..13)1..2 blockwise direct sum code[128X[104X
[4X[32X[104X
[1X6.2-9 ConstructionXCode[101X
[29X[2XConstructionXCode[102X( [3XC[103X, [3XA[103X ) [32X function
[33X[0;0YConsider a list of [22Xj[122X linear codes of the same length [22XN[122X over the same field
[22XF[122X, [22XC = { C_1, C_2, ..., C_j }[122X, where the parameter of the [22Xi[122Xth code is [22XC_i =
[N, K_i, D_i][122X and [22XC_j ⊂ C_j-1 ⊂ ... ⊂ C_2 ⊂ C_1[122X. Consider a list of [22Xj-1[122X
auxiliary linear codes of the same field [22XF[122X, [22XA = { A_1, A_2, ..., A_j-1 }[122X
where the parameter of the [22Xi[122Xth code [22XA_i[122X is [22X[n_i, k_i=(K_i-K_i+1), d_i][122X, an
[22X[n, K_1, d][122X linear code over field [22XF[122X can be constructed where [22Xn = N +
∑_i=1^j-1 n_i[122X, and [22Xd = min{ D_j, D_j-1 + d_j-1, D_j-2 + d_j-2 + d_j-1, ...,
D_1 + ∑_i=1^j-1 d_i}[122X.[133X
[33X[0;0YFor more information on Construction X, refer to [SRC72].[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27XC1 := BCHCode(127, 43);[127X[104X
[4X[28Xa cyclic [127,29,43]31..59 BCH code, delta=43, b=1 over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC2 := BCHCode(127, 47);[127X[104X
[4X[28Xa cyclic [127,22,47..51]36..63 BCH code, delta=47, b=1 over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC3 := BCHCode(127, 55);[127X[104X
[4X[28Xa cyclic [127,15,55]41..62 BCH code, delta=55, b=1 over GF(2)[128X[104X
[4X[25Xgap>[125X [27XG1 := ShallowCopy( GeneratorMat(C2) );;[127X[104X
[4X[25Xgap>[125X [27XAppend(G1, [ GeneratorMat(C1)[23] ]);;[127X[104X
[4X[25Xgap>[125X [27XC1 := GeneratorMatCode(G1, GF(2));[127X[104X
[4X[28Xa linear [127,23,1..43]35..63 code defined by generator matrix over GF(2)[128X[104X
[4X[25Xgap>[125X [27XMinimumDistance(C1);[127X[104X
[4X[28X43[128X[104X
[4X[25Xgap>[125X [27XC := [ C1, C2, C3 ];[127X[104X
[4X[28X[ a linear [127,23,43]35..63 code defined by generator matrix over GF(2), [128X[104X
[4X[28X a cyclic [127,22,47..51]36..63 BCH code, delta=47, b=1 over GF(2), [128X[104X
[4X[28X a cyclic [127,15,55]41..62 BCH code, delta=55, b=1 over GF(2) ][128X[104X
[4X[25Xgap>[125X [27XIsSubset(C[1], C[2]);[127X[104X
[4X[28Xtrue[128X[104X
[4X[25Xgap>[125X [27XIsSubset(C[2], C[3]);[127X[104X
[4X[28Xtrue[128X[104X
[4X[25Xgap>[125X [27XA := [ RepetitionCode(4, GF(2)), EvenWeightSubcode( QRCode(17, GF(2)) ) ];[127X[104X
[4X[28X[ a cyclic [4,1,4]2 repetition code over GF(2), a cyclic [17,8,6]3..6 even weight subcode ][128X[104X
[4X[25Xgap>[125X [27XCX := ConstructionXCode(C, A);[127X[104X
[4X[28Xa linear [148,23,53]43..74 Construction X code[128X[104X
[4X[25Xgap>[125X [27XHistory(CX);[127X[104X
[4X[28X[ "a linear [148,23,53]43..74 Construction X code of", [128X[104X
[4X[28X "Base codes: [ a cyclic [127,15,55]41..62 BCH code, delta=55, b=1 over GF(2)\[128X[104X
[4X[28X, a cyclic [127,22,47..51]36..63 BCH code, delta=47, b=1 over GF(2), a linear \[128X[104X
[4X[28X[127,23,43]35..63 code defined by generator matrix over GF(2) ]", [128X[104X
[4X[28X "Auxiliary codes: [ a cyclic [4,1,4]2 repetition code over GF(2), a cyclic [\[128X[104X
[4X[28X17,8,6]3..6 even weight subcode ]" ][128X[104X
[4X[32X[104X
[1X6.2-10 ConstructionXXCode[101X
[29X[2XConstructionXXCode[102X( [3XC1[103X, [3XC2[103X, [3XC3[103X, [3XA1[103X, [3XA2[103X ) [32X function
[33X[0;0YConsider a set of linear codes over field [22XF[122X of the same length, [22Xn[122X, [22XC_1=[n,
k_1, d_1][122X, [22XC_2=[n, k_2, d_2][122X and [22XC_3=[n, k_3, d_3][122X such that [22XC_2 ⊂ C_1[122X, [22XC_3
⊂ C_1[122X and [22XC_4 = C_2 ∩ C_3[122X. Given two auxiliary codes [22XA_1=[n_1, k_1-k_2, e_1][122X
and [22XA_2=[n_2, k_1-k_3, e_2][122X over the same field [22XF[122X, there exists an
[22X[n+n_1+n_2, k_1, d][122X linear code [22XC_XX[122X over field [22XF[122X, where [22Xd = min{d_4, d_3 +
e_1, d_2 + e_2, d_1 + e_1 + e_2}[122X.[133X
[33X[0;0YThe codewords of [22XC_XX[122X can be partitioned into three sections [22X( v | a | b )[122X
where [22Xv[122X has length [22Xn[122X, [22Xa[122X has length [22Xn_1[122X and [22Xb[122X has length [22Xn_2[122X. A codeword from
Construction XX takes the following form:[133X
[30X [33X[0;6Y[22X( v | 0 | 0 )[122X if [22Xv ∈ C_4[122X[133X
[30X [33X[0;6Y[22X( v | a_1 | 0 )[122X if [22Xv ∈ C_3 backslash C_4[122X[133X
[30X [33X[0;6Y[22X( v | 0 | a_2 )[122X if [22Xv ∈ C_2 backslash C_4[122X[133X
[30X [33X[0;6Y[22X( v | a_1 | a_2 )[122X otherwise[133X
[33X[0;0YFor more information on Construction XX, refer to [All84].[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27Xa := PrimitiveRoot(GF(32));[127X[104X
[4X[28XZ(2^5)[128X[104X
[4X[25Xgap>[125X [27Xf0 := MinimalPolynomial( GF(2), a^0 );[127X[104X
[4X[28Xx_1+Z(2)^0[128X[104X
[4X[25Xgap>[125X [27Xf1 := MinimalPolynomial( GF(2), a^1 );[127X[104X
[4X[28Xx_1^5+x_1^2+Z(2)^0[128X[104X
[4X[25Xgap>[125X [27Xf5 := MinimalPolynomial( GF(2), a^5 );[127X[104X
[4X[28Xx_1^5+x_1^4+x_1^2+x_1+Z(2)^0[128X[104X
[4X[25Xgap>[125X [27XC2 := CheckPolCode( f0 * f1, 31, GF(2) );; MinimumDistance(C2);; Display(C2);[127X[104X
[4X[28Xa cyclic [31,6,15]10..13 code defined by check polynomial over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC3 := CheckPolCode( f0 * f5, 31, GF(2) );; MinimumDistance(C3);; Display(C3);[127X[104X
[4X[28Xa cyclic [31,6,15]10..13 code defined by check polynomial over GF(2)[128X[104X
[4X[25Xgap>[125X [27XC1 := UnionCode(C2, C3);; MinimumDistance(C1);; Display(C1);[127X[104X
[4X[28Xa linear [31,11,11]7..11 union code of[128X[104X
[4X[28XU: a cyclic [31,6,15]10..13 code defined by check polynomial over GF(2)[128X[104X
[4X[28XV: a cyclic [31,6,15]10..13 code defined by check polynomial over GF(2)[128X[104X
[4X[25Xgap>[125X [27XA1 := BestKnownLinearCode( 10, 5, GF(2) );[127X[104X
[4X[28Xa linear [10,5,4]2..4 shortened code[128X[104X
[4X[25Xgap>[125X [27XA2 := DualCode( RepetitionCode(6, GF(2)) );[127X[104X
[4X[28Xa cyclic [6,5,2]1 dual code[128X[104X
[4X[25Xgap>[125X [27XCXX:= ConstructionXXCode(C1, C2, C3, A1, A2 );[127X[104X
[4X[28Xa linear [47,11,15..17]13..23 Construction XX code[128X[104X
[4X[25Xgap>[125X [27XMinimumDistance(CXX);[127X[104X
[4X[28X17[128X[104X
[4X[25Xgap>[125X [27XHistory(CXX); [127X[104X
[4X[28X[ "a linear [47,11,17]13..23 Construction XX code of", [128X[104X
[4X[28X "C1: a cyclic [31,11,11]7..11 union code", [128X[104X
[4X[28X "C2: a cyclic [31,6,15]10..13 code defined by check polynomial over GF(2)", [128X[104X
[4X[28X "C3: a cyclic [31,6,15]10..13 code defined by check polynomial over GF(2)", [128X[104X
[4X[28X "A1: a linear [10,5,4]2..4 shortened code", [128X[104X
[4X[28X "A2: a cyclic [6,5,2]1 dual code" ][128X[104X
[4X[32X[104X
[1X6.2-11 BZCode[101X
[29X[2XBZCode[102X( [3XO[103X, [3XI[103X ) [32X function
[33X[0;0YGiven a set of outer codes of the same length [22XO_i = [N, K_i, D_i][122X over
GF([22Xq^e_i[122X), where [22Xi=1,2,...,t[122X and a set of inner codes of the same length [22XI_i
= [n, k_i, d_i][122X over GF([22Xq[122X), [10XBZCode[110X returns a Blokh-Zyablov multilevel
concatenated code with parameter [22X[ n × N, ∑_i=1^t e_i × K_i,
min_i=1,...,t{d_i × D_i} ][122X over GF([22Xq[122X).[133X
[33X[0;0YNote that the set of inner codes must satisfy chain condition, i.e. [22XI_1 =
[n, k_1, d_1] ⊂ I_2=[n, k_2, d_2] ⊂ ... ⊂ I_t=[n, k_t, d_t][122X where [22X0=k_0 <
k_1 < k_2 < ... < k_t[122X. The dimension of the inner codes must satisfy the
condition [22Xe_i = k_i - k_i-1[122X, where GF([22Xq^e_i[122X) is the field of the [22Xi[122Xth outer
code.[133X
[33X[0;0YFor more information on Blokh-Zyablov multilevel concatenated code, refer to
[Bro98].[133X
[1X6.2-12 BZCodeNC[101X
[29X[2XBZCodeNC[102X( [3XO[103X, [3XI[103X ) [32X function
[33X[0;0YThis function is the same as [10XBZCode[110X, except this version is faster as it
does not estimate the covering radius of the code. Users are encouraged to
use this version unless you are working on very small codes.[133X
[4X[32X Example [32X[104X
[4X[25Xgap>[125X [27X#[127X[104X
[4X[25Xgap>[125X [27X# Binary code[127X[104X
[4X[25Xgap>[125X [27X#[127X[104X
[4X[25Xgap>[125X [27XO := [ CyclicMDSCode(2,3,7), BestKnownLinearCode(9,5,GF(2)), CyclicMDSCode(2,3,4) ];[127X[104X
[4X[28X[ a cyclic [9,7,3]1 MDS code over GF(8), a linear [9,5,3]2..3 shortened code, [128X[104X
[4X[28X a cyclic [9,4,6]4..5 MDS code over GF(8) ][128X[104X
[4X[25Xgap>[125X [27XA := ExtendedCode( HammingCode(3,GF(2)) );;[127X[104X
[4X[25Xgap>[125X [27XI := [ SubCode(A), A, DualCode( RepetitionCode(8, GF(2)) ) ];[127X[104X
[4X[28X[ a linear [8,3,4]3..4 subcode, a linear [8,4,4]2 extended code, a cyclic [8,7,2]1 dual code ][128X[104X
[4X[25Xgap>[125X [27XC := BZCodeNC(O, I);[127X[104X
[4X[28Xa linear [72,38,12]0..72 Blokh Zyablov concatenated code[128X[104X
[4X[25Xgap>[125X [27X#[127X[104X
[4X[25Xgap>[125X [27X# Non binary code[127X[104X
[4X[25Xgap>[125X [27X#[127X[104X
[4X[25Xgap>[125X [27XO2 := ExtendedCode(GoppaCode(ConwayPolynomial(5,2), Elements(GF(5))));;[127X[104X
[4X[25Xgap>[125X [27XO3 := ExtendedCode(GoppaCode(ConwayPolynomial(5,3), Elements(GF(5))));;[127X[104X
[4X[25Xgap>[125X [27XO1 := DualCode( O3 );;[127X[104X
[4X[25Xgap>[125X [27XMinimumDistance(O1);; MinimumDistance(O2);; MinimumDistance(O3);;[127X[104X
[4X[25Xgap>[125X [27XCy := CyclicCodes(5, GF(5));;[127X[104X
[4X[25Xgap>[125X [27Xfor i in [4, 5] do; MinimumDistance(Cy[i]);; od;[127X[104X
[4X[25Xgap>[125X [27XO := [ O1, O2, O3 ];[127X[104X
[4X[28X[ a linear [6,4,3]1 dual code, a linear [6,3,4]2..3 extended code,[128X[104X
[4X[28X a linear [6,2,5]3..4 extended code ][128X[104X
[4X[25Xgap>[125X [27XI := [ Cy[5], Cy[4], Cy[3] ];[127X[104X
[4X[28X[ a cyclic [5,1,5]3..4 enumerated code over GF(5),[128X[104X
[4X[28X a cyclic [5,2,4]2..3 enumerated code over GF(5),[128X[104X
[4X[28X a cyclic [5,3,1..3]2 enumerated code over GF(5) ][128X[104X
[4X[25Xgap>[125X [27XC := BZCodeNC( O, I );[127X[104X
[4X[28Xa linear [30,9,5..15]0..30 Blokh Zyablov concatenated code[128X[104X
[4X[25Xgap>[125X [27XMinimumDistance(C);[127X[104X
[4X[28X15[128X[104X
[4X[25Xgap>[125X [27XHistory(C);[127X[104X
[4X[28X[ "a linear [30,9,15]0..30 Blokh Zyablov concatenated code of",[128X[104X
[4X[28X "Inner codes: [ a cyclic [5,1,5]3..4 enumerated code over GF(5), a cyclic [5\[128X[104X
[4X[28X,2,4]2..3 enumerated code over GF(5), a cyclic [5,3,1..3]2 enumerated code ove\[128X[104X
[4X[28Xr GF(5) ]",[128X[104X
[4X[28X "Outer codes: [ a linear [6,4,3]1 dual code, a linear [6,3,4]2..3 extended c\[128X[104X
[4X[28Xode, a linear [6,2,5]3..4 extended code ]" ][128X[104X
[4X[32X[104X
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