substitute(ChainComplex,Ring) -- Substitute a chain complex to a new ring.

i1 : R=QQ[x_1..x_4,z_1];

i2 : cc=res ideal(x_4*x_3, -x_1*x_2+x_4*z_1);

i3 : cs=substitute(cc,QQ[x_1..x_4])

                         1                         2                         1
o3 = (QQ[x , x , x , x ])  <-- (QQ[x , x , x , x ])  <-- (QQ[x , x , x , x ])  <-- 0
          1   2   3   4             1   2   3   4             1   2   3   4         
                                                                                   3
     0                         1                         2

o3 : ChainComplex

i4 : print cs.dd_1
| x_1x_2 x_3x_4 |