Description
dd -- a symbol used as a key in a chain complex, under which are stored the differentials.
The differentials are stored as the members in a chain complex map of degree
-1. The map
C.dd_i is the one whose source is the module
C_i, and it is arranged to be zero if no map has been stored in that spot.
i1 : R = ZZ/101[a,b];
|
i2 : C = resolution cokernel vars R
1 2 1
o2 = R <-- R <-- R <-- 0
0 1 2 3
o2 : ChainComplex
|
i3 : C.dd
1 2
o3 = 0 : R <----------- R : 1
| a b |
2 1
1 : R <-------------- R : 2
{1} | -b |
{1} | a |
1
2 : R <----- 0 : 3
0
o3 : ChainComplexMap
|
i4 : C.dd_2
o4 = {1} | -b |
{1} | a |
2 1
o4 : Matrix R <-- R
|