delta[i,j] - Predefined Kronecker delta
Synopsis:
Examples:
> delta[1,1];
1
> delta[1,2];
0
> A[i,j] &t delta[j,k] &t b[k,n];
A[i, 1] b[1, n] + A[i, 2] b[2, n] + A[i, 3] b[3, n]