<Verb>CocycleCondition(R,n):: FreeRes, Int --> IntMat</Verb><P/>
Inputs a free <M>\mathbb ZG</M>-resolution <M>R</M> of <M>\mathbb Z</M>
and an integer
<M>n \ge 1</M>.
It returns an integer matrix <M>M</M> with the following property.
Let <M>d</M> be the <M>\mathbb ZG</M>-rank of <M>R_n</M>.
An integer vector <M>f=[f_1, ... , f_d]</M> then represents a
<M>\mathbb ZG</M>-homomorphism <M>R_n \rightarrow
\mathbb Z_q</M> which sends the
<M>i</M>th generator of <M>R_n</M> to the integer <M>f_i</M> in the trivial
<M>\mathbb ZG</M>-module <M>\mathbb Z_q=\mathbb Z/q{\mathbb Z}</M>
(where possibly <M>q=0</M>). The homomorphism <M>f</M> is a cocycle if and
only if <M>M^tf=0</M> mod <M>q</M>.
