iszero and == for spoly in quotient ring

deps/src/ideals.cpp

@@ -15,6 +15,13 @@ auto id_sres_helper(sip_sideal * m, int n, ring R)
     return std::make_tuple(s, minimal);
 }
 
+auto qring_simplify_helper(poly p, ring R)
+{
+  if (R->qideal==NULL)
+    return p_Copy(p,R);
+  else
+    return p_Copy(jj_NormalizeQRingP(p_Copy(p,R),R),R);
+}
 
 auto id_fres_helper(sip_sideal * I, int n, std::string method, ring R)
 {
@@ -722,4 +729,5 @@ void singular_define_ideals(jlcxx::Module & Singular)
         }
         return res;
     });
+    Singular.method("qring_simplify", &qring_simplify_helper);
 }

deps/src/rings.cpp

@@ -344,6 +344,7 @@ void singular_define_rings(jlcxx::Module & Singular)
     });
     Singular.method("rCopy", rCopy);
     Singular.method("r_get_qideal", [](ring r) {return r->qideal;});
+    Singular.method("is_qring", [](ring r) {return bool(r->qideal!=NULL);});
     Singular.method("rQuotientRing", [](ideal i, ring r) {
         // This looks too simple, try make_qring if it doesn't work.
         ring Q = rCopy(r);

src/poly/poly.jl

@@ -140,7 +140,14 @@ function one(R::PolyRingUnion)
 end
 
 function iszero(p::SPolyUnion)
-   GC.@preserve p p.ptr.cpp_object == C_NULL
+   R = parent(p)
+   if libSingular.is_qring(R.ptr)
+     GC.@preserve p x = libSingular.qring_simplify(p.ptr,R.ptr)
+     xx = R(x)
+     return xx.ptr.cpp_object == C_NULL
+   else
+     return p.ptr.cpp_object == C_NULL
+   end
 end
 
 function isone(p::SPolyUnion)
@@ -711,7 +718,7 @@ end
 
 function (x::SPolyUnion{T} == y::SPolyUnion{T}) where T <: Nemo.RingElem
    check_parent(x, y)
-   GC.@preserve x y return Bool(libSingular.p_EqualPolys(x.ptr, y.ptr, parent(x).ptr))
+   return(iszero(x-y))
 end
 
 function Base.isless(x::SPolyUnion{T}, y::SPolyUnion{T}) where T <: Nemo.RingElem

test/poly/poly-test.jl

@@ -234,6 +234,13 @@ end
    @test trailing_coefficient(R()) == 0
 end
 
+@testset "poly.QuotientRing" begin
+    R, (x,y) = polynomial_ring(QQ, ["x", "y"])
+    Q, (a,b) = QuotientRing(R, Ideal(R, x-y))
+    @test iszero(a-b)
+    @test (a-b)==Q(0)
+end
+
 @testset "poly.change_base_ring" begin
    R1, (x, ) = polynomial_ring(ZZ, ["x", ])