Procedure from library brnoeth.lib (see brnoeth_lib).
Usage:
sys_code(C); C is a matrix of constants
Return:
list L with:
L[1] is the generator matrix in standard form of an equivalent code,
L[2] is the parity check matrix in standard form of such code,
L[3] is an intvec which represents the needed permutation.
Note:
Computes a systematic code which is equivalent to the given one.
The input should be a matrix of numbers.
The output has to be interpreted as follows: if the input was
the generator matrix of an AG code then one should apply the
permutation L[3] to the divisor D of rational points by means
of permute_L(D,L[3]); before continuing to work with the
code (for instance, if you want to use the systematic encoding
together with a decoding algorithm).