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Relax signature of ==(::MPolyIdeal, ::MPolyIdeal) #2937

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Oct 19, 2023
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Relax signature of ==(::MPolyIdeal, ::MPolyIdeal) #2937

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4 changes: 2 additions & 2 deletions docs/src/CommutativeAlgebra/ideals.md
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Expand Up @@ -167,13 +167,13 @@ is_monomial(f::MPolyRingElem)
### Containment of Ideals

```@docs
is_subset(I::MPolyIdeal{T}, J::MPolyIdeal{T}) where T
is_subset(I::MPolyIdeal, J::MPolyIdeal)
```

### Equality of Ideals

```@docs
==(I::MPolyIdeal{T}, J::MPolyIdeal{T}) where T
==(I::MPolyIdeal, J::MPolyIdeal)
```

### Ideal Membership
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14 changes: 8 additions & 6 deletions src/Rings/mpoly-ideals.jl
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Expand Up @@ -66,11 +66,11 @@ end

# elementary operations #######################################################
@doc raw"""
check_base_rings(I::MPolyIdeal{T}, J::MPolyIdeal{T}) where T
check_base_rings(I::MPolyIdeal, J::MPolyIdeal)

Throws an error if the base rings of the ideals `I` and `J` do not coincide.
"""
function check_base_rings(I::MPolyIdeal{T}, J::MPolyIdeal{T}) where T
function check_base_rings(I::MPolyIdeal, J::MPolyIdeal)
if !isequal(base_ring(I), base_ring(J))
error("Base rings must coincide.")
end
Expand Down Expand Up @@ -970,7 +970,7 @@ end

#######################################################
@doc raw"""
==(I::MPolyIdeal{T}, J::MPolyIdeal{T}) where T
==(I::MPolyIdeal, J::MPolyIdeal)

Return `true` if `I` is equal to `J`, `false` otherwise.

Expand All @@ -989,7 +989,8 @@ julia> I == J
false
```
"""
function ==(I::MPolyIdeal{T}, J::MPolyIdeal{T}) where T
function ==(I::MPolyIdeal, J::MPolyIdeal)
check_base_rings(I, J)
I === J && return true
gens(I) == gens(J) && return true
return issubset(I, J) && issubset(J, I)
Expand All @@ -999,7 +1000,7 @@ end

#######################################################
@doc raw"""
is_subset(I::MPolyIdeal{T}, J::MPolyIdeal{T}) where T
is_subset(I::MPolyIdeal, J::MPolyIdeal)

Return `true` if `I` is contained in `J`, `false` otherwise.

Expand All @@ -1018,7 +1019,8 @@ julia> is_subset(I, J)
true
```
"""
function is_subset(I::MPolyIdeal{T}, J::MPolyIdeal{T}) where T
function is_subset(I::MPolyIdeal, J::MPolyIdeal)
check_base_rings(I, J)
return Singular.iszero(Singular.reduce(singular_generators(I), singular_groebner_generators(J)))
end

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15 changes: 8 additions & 7 deletions test/Rings/mpoly-graded.jl
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Expand Up @@ -421,7 +421,7 @@ end



@testset "homogenizaton: big principal ideal" begin
@testset "homogenization: big principal ideal" begin
# It is easy to honogenize a principal ideal: just homogenize the gen!
# Do not really need lots of vars; just a "large" single polynomial
LotsOfVars = 250;
Expand Down Expand Up @@ -463,42 +463,43 @@ end
x^3*y^2+x*y*z^3+x*y+y^2,
x^2*y^3*w+y^3*z^2*w-y*z^3*w^2-y*w^2], W1, "h");
Ih_std = homogenization(I, "h")
Ih_expected = ideal(Ih_W1)
Ih_expected = ideal(base_ring(Ih_std), Ih_W1)
@test Ih_std == Ih_expected
Ih = homogenization(I, W1, "h")
Ih_expected = ideal(base_ring(Ih), Ih_W1)
@test Ih == Ih_expected
Ih_W2 = homogenization([x*y*z^3+x^3*y^2+y^2+x*y,
x*y*z^2*w+x^3*w^2+x^3*y*w+w^2,
x^3*z*w^2+x^3*y*z*w-x^3*y^2*w+z*w^2-y^2*w-x*y*w,
x^5*w^3+x^3*y^3*z*w-y*z^2*w^2+2*x^5*y*w^2+x^2*w^3+x^5*y^2*w+y^3*z*w+x*y^2*z*w+x^2*y*w^2,
y*z^3*w^2-y^3*z^2*w-x^2*y^3*w+y*w^2],
W2, "h");
Ih_expected = ideal(Ih_W2)
Ih = homogenization(I, W2, "h")
Ih_expected = ideal(base_ring(Ih), Ih_W2)
@test Ih == Ih_expected
Ih_W3 = homogenization([x^2*y^3*w+y^3*z^2*w-y*z^3*w^2-y*w^2,
x^3*y*w+x*y*z^2*w+x^3*w^2+w^2,
x^3*y^2+y^2+x*y*z^3+x*y],
W3, "h");
Ih_expected = ideal(Ih_W3)
Ih = homogenization(I, W3, "h")
Ih_expected = ideal(base_ring(Ih), Ih_W3)
@test Ih == Ih_expected
# Ih_W4 = ????
# Ih_expected = ideal(Ih_W4)
# Ih = homogenization(I, W4, "h")
# Ih_expected = ideal(base_ring(Ih), Ih_W4)
# @test Ih = Ih_expected
Ih_W2a = homogenization([x*y*z^3+x^3*y^2+y^2+x*y,
x*y*z^2*w+x^3*w^2+x^3*y*w+w^2,
x^3*z*w^2+x^3*y*z*w-x^3*y^2*w+z*w^2-y^2*w-x*y*w,
y*z^3*w^2-y^3*z^2*w-x^2*y^3*w+y*w^2,
x^5*w^3+x^3*y^3*z*w-y*z^2*w^2+2*x^5*y*w^2+x^2*w^3+x^5*y^2*w+y^3*z*w+x*y^2*z*w+x^2*y*w^2],
W2a, "h");
Ih_expected = ideal(Ih_W2a)
Ih = homogenization(I, W2a, "h")
Ih_expected = ideal(base_ring(Ih), Ih_W2a)
@test Ih == Ih_expected
# Ih_W2b = ????
# Ih_expected = ideal(Ih_W2b)
# Ih = homogenization(I, W2b, "h")
# Ih_expected = ideal(base_ring(Ih), Ih_W2b)
# @test Ih == Ih_expected
end

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7 changes: 7 additions & 0 deletions test/Rings/mpoly.jl
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Expand Up @@ -85,6 +85,13 @@ end
@test intersect(I,J,P) == ideal(R,[x^2*y^2, x^4, x*y^4])
@test intersect(I,J,P) == intersect([I,J,P])

@test I != J
RR, (xx, yy) = grade(R, [1, 1])
@test_throws ErrorException ideal(R, [x]) == ideal(RR, [xx])
@test is_subset(I, I)
RR, (xx, yy) = polynomial_ring(QQ, ["xx", "yy"])
@test_throws ErrorException is_subset(ideal(R, [x]), ideal(RR, [xx]))

f = x^2 + y^2
g = x^4*y - x*y^3
I = [f, g]
Expand Down