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D.10.2.9 errorRand

Procedure from library decodegb.lib (see decodegb_lib).

Usage:
errorRand(y, num, e); y is matrix, num,e are int
 
          - y is a (code) word,
          - num is the number of errors,
          - e is an extension degree (if one wants values to be from GF(p^e))

Return:
corresponding received word

Example:
 
LIB "decodegb.lib";
//correct 2 errors in [7,3] 8-ary code RS code
int t=2; int q=8; int n=7; int redun=4;
ring r=(q,a),x,dp;
matrix h_full=genMDSMat(n,a);
matrix h=submat(h_full,1..redun,1..n);
matrix g=dual_code(h);
matrix x[1][3]=0,0,1,0;
matrix y[1][7]=encode(x,g);
//disturb with 2 random errors
matrix rec[1][7]=errorRand(y,2,3);
print(rec);
==> a3,a6,a2,a,0,0,1
print(rec-y);
==> a4,0,a5,0,0,0,0