
D.7.3.13 ReynoldsOperator
Procedure from library rinvar.lib (see rinvar_lib).
 Usage:
 ReynoldsOperator(G, action [, opt]); ideal G, action; int opt
 Purpose:
 compute the Reynolds operator of the group G which acts via 'action'
 Return:
 polynomial ring R over a simple extension of the ground field of the
basering (the extension might be trivial), containing a list
'ROelements', the ideals 'id', 'actionid' and the polynomial 'newA'.
R = K(a)[s(1..r),t(1..n)].
 'ROelements' is a list of ideals, each ideal represents a
substitution map F : R > R according to the zeroset of G
 'id' is the ideal of G in the new ring
 'newA' is the new representation of a' in terms of a. If the
basering does not contain a parameter then 'newA' = 'a'.
 Assume:
 basering = K[s(1..r),t(1..n)], K = Q or K = Q(a') and minpoly != 0,
G is the ideal of a finite group in K[s(1..r)], 'action' is a linear
group action of G
