the script returns the dual of the complex F obtained by resolving the cokernel of the transpose of the presentation of M for len steps. Thus M is the len-th syzygy of the module resolved by F. When the first argument len is omitted, the value defaults to len = 2.
i1 : S = ZZ/101[a,b,c]; |
i2 : R = S/ideal"a3,b3,c3"; |
i3 : M = module ideal vars R; |
i4 : betti presentation M
0 1
o4 = total: 3 6
1: 3 3
2: . 3
o4 : BettiTally
|
i5 : betti (F = cosyzygyRes(3,M))
0 1 2 3 4
o5 = total: 3 1 1 3 6
-7: 3 1 . . .
-6: . . . . .
-5: . . . . .
-4: . . . . .
-3: . . . . .
-2: . . 1 3 3
-1: . . . . 3
o5 : BettiTally
|
i6 : cosyzygyRes M
1 1 3 6
o6 = R <-- R <-- R <-- R
0 1 2 3
o6 : ChainComplex
|
The object cosyzygyRes is a method function.