Description
If the source and target of
f are graded, then minimal presentations of the source and target modules for
f are computed using
minimalPresentation(Module) and
g is the matrix corresponding to
f with source and target the minimally presented source and target. If either the source or target of
f is not graded then an attempt is made to improve their presentations and
gis the matrix with resulting source and target. An example follows.
i1 : R = ZZ/32003[a..d];
|
i2 : f = inducedMap(coker matrix {{a,1,b},{c,3,b+d}},R^2)
o2 = | 1 -10668 |
| 0 0 |
o2 : Matrix
|
i3 : g = prune f
o3 = | -3 1 |
o3 : Matrix
|
i4 : source g
2
o4 = R
o4 : R-module, free
|
i5 : target g
o5 = cokernel | b+16001d a-10668c |
1
o5 : R-module, quotient of R
|
This function does not remove elements from the base field from the matrix, but rather minimally presents the source and target and gives the corresponding new map. For example:
i6 : m = matrix{{a,1,b},{c,3,b+d}}
o6 = | a 1 b |
| c 3 b+d |
2 3
o6 : Matrix R <-- R
|
i7 : prune m
o7 = | a 1 b |
| c 3 b+d |
2 3
o7 : Matrix R <-- R
|
Unlike above, nothing changes.