RingHom EvalHom(const PolyRing& Rx, const BigRat& q) // Maps f in R[x] into f(q) in R
{
if (NumIndets(Rx) != 1) CoCoA_ERROR(ERR::BadArg, "EvalHom(Rx,N)");
const ring& R = CoeffRing(Rx);
const vector<RingElem> IndetImage(1, RingElem(R,q));
return Rx->myHomCtor(R, IdentityHom(R), IndetImage);
}
RingHom EvalHom(const PolyRing& Rx, ConstRefRingElem r) // Maps f in R[x] into f(r) in R
{
if (NumIndets(Rx) != 1) CoCoA_ERROR(ERR::BadArg, "EvalHom(Rx,r)");
const ring& R = CoeffRing(Rx);
if (owner(r) != R) CoCoA_ERROR(ERR::MixedRings, "EvalHom(Rx,r");
const vector<RingElem> IndetImage(1, r);
return Rx->myHomCtor(R, IdentityHom(R), IndetImage);
}
RingHom EvalHom(const PolyRing& Rx, const std::vector<RingElem>& IndetImages)
{
const char* const FnName = "EvalHom(Rx,IndetImages)";
const ring& R = CoeffRing(Rx);
if (NumIndets(Rx) != len(IndetImages))
CoCoA_ERROR(ERR::BadPolyRingHomImages, FnName);
for (long i=0; i < NumIndets(Rx); ++i)
if (owner(IndetImages[i]) != R)
CoCoA_ERROR(ERR::BadPolyRingHomImages, FnName);
return Rx->myHomCtor(R, IdentityHom(R), IndetImages);
}
// Rx is the domain, S is the codomain
RingHom PolyRingHom(const PolyRing& Rx, const ring& S, RingHom CoeffHom, const std::vector<RingElem>& IndetImages)
{
const char* const FnName = "PolyRingHom(Rx,S,CoeffHom,IndetImages)";
if (domain(CoeffHom) != CoeffRing(Rx))
CoCoA_ERROR(ERR::MixedCoeffRings, FnName);
if (IsPolyRing(S) && codomain(CoeffHom) == CoeffRing(S))
CoeffHom = CoeffEmbeddingHom(S)(CoeffHom);
if (codomain(CoeffHom) != S)
CoCoA_ERROR(ERR::BadCodomain, FnName);
if (NumIndets(Rx) != len(IndetImages))
CoCoA_ERROR(ERR::BadPolyRingHomImages, FnName);
for (long i=0; i < NumIndets(Rx); ++i)
if (owner(IndetImages[i]) != S)
CoCoA_ERROR(ERR::BadPolyRingHomImages, FnName);
return Rx->myHomCtor(S, CoeffHom, IndetImages);
}
RingHom PolyAlgebraHom(const PolyRing& Rx, const ring& Ry, const std::vector<RingElem>& IndetImages)
{
const char* const FnName = "PolyAlgebraHom(Rx,Ry,IndetImages)";
// Check that IndetImages are sensible...
if (NumIndets(Rx) != len(IndetImages))
CoCoA_ERROR(ERR::BadPolyRingHomImages, FnName);
for (long i=0; i < NumIndets(Rx); ++i)
if (owner(IndetImages[i]) != Ry)
CoCoA_ERROR(ERR::BadPolyRingHomImages, FnName);
// // Special case: codomain is coeff ring.
// if (Ry == CoeffRing(Rx))
// return Rx->myHomCtor(Ry, IdentityHom(Ry), IndetImages);
// // General case: codomain must be a poly ring with same coeffs
// if (!IsPolyRing(Ry))
// CoCoA_ERROR(ERR::BadCodomain, FnName);
// if (CoeffRing(Rx) != CoeffRing(Ry))
// CoCoA_ERROR(ERR::MixedCoeffRings, FnName);
// return Rx->myHomCtor(Ry, CoeffEmbeddingHom(Ry), IndetImages);
return Rx->myHomCtor(Ry, CanonicalHom(CoeffRing(Rx),Ry), IndetImages);
}
