HomToIntegralModule(R,A):: FreeResolution, GroupHomomorphism --> CochainComplex

Inputs a free \mathbb ZG-resolution R in characteristic 0 and a group homomorphism A\colon G \rightarrow {\rm GL}_n(\mathbb Z). The homomorphism A can be viewed as the \mathbb ZG-module with underlying abelian group \mathbb Z^n on which G acts via the homomorphism A. It returns the cochain complex Hom_{\mathbb ZG}(R,A).