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minimalPresentation(Matrix) -- minimally present source and target of a matrix

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.

Caveat

Check out the example just above.