extendFromMiddle -- extends a map between ChainComplexes

Synopsis

Usage:

m = extendFromMiddle(F1,F2,f,i)
Inputs:
- F1, a chain complex,
- F2, a chain complex,
- f, a matrix, homomorphism from F2_0 to F1_i
- i, an integer,
Outputs:
- m, a chain complex map,

Description

If f is a map to F1_i from F2_0, the script computes a ChainComplexMap to F1 from F2e, where F2e is a chain complex obtained from F2 by prepending zeros.

Caveat

the process of making a new ChainComplex seems to destroy the direct sum information in the source and target modules.

Ways to use extendFromMiddle :

extendFromMiddle(ChainComplex,ChainComplex,Matrix,ZZ)

For the programmer

The object extendFromMiddle is a method function.