Generic.ideal: add is_subset, deprecate contains

The `contains` methods for ideals were just a wrong choice of API:
`contains(,b)` is meant to test if `b` is an *element* of `a`, not a
subset.

Author: fingolfin

docs/src/ideal.md

@@ -116,7 +116,7 @@ ideals.
 ### Containment
 
 ```@docs
-contains(::Generic.Ideal{T}, ::Generic.Ideal{T}) where T <: RingElement
+is_subset(::Generic.Ideal{T}, ::Generic.Ideal{T}) where T <: RingElement
 ```
 
 ```@docs
@@ -146,10 +146,10 @@ AbstractAlgebra.Generic.Ideal{AbstractAlgebra.Generic.Poly{BigInt}}(Univariate p
 julia> J = Generic.Ideal(R, W)
 AbstractAlgebra.Generic.Ideal{AbstractAlgebra.Generic.Poly{BigInt}}(Univariate polynomial ring in x over integers, AbstractAlgebra.Generic.Poly{BigInt}[282, 3*x + 255, x^2 + 107])
 
-julia> contains(J, I)
+julia> is_subset(I, J)
 false
 
-julia> contains(I, J)
+julia> is_subset(J, I)
 true
 
 julia> intersect(I, J) == J

src/Deprecations.jl

@@ -62,3 +62,7 @@ end
 
 # deprecated in 0.45.0
 @deprecate test_iterate ConformanceTests.test_iterate
+
+# deprecated in 0.45.2
+import Base: contains
+@deprecate contains(I::Ideal{T}, J::Ideal{T}) where {T <: RingElement} issubset(J, I)

src/generic/Ideal.jl

@@ -2113,30 +2113,12 @@ function Base.in(v::T, I::Ideal{T}) where T <: RingElement
 end
 
 @doc raw"""
-    Base.contains(I::Ideal{T}, J::Ideal{T}) where T <: RingElement
+    Base.issubset(I::Ideal{T}, J::Ideal{T}) where T <: RingElement
 
-Return `true` if the ideal `J` is contained in the ideal `I`.
+Return `true` if the ideal `I` is a subset of the ideal `J`.
 """
-function Base.contains(I::Ideal{T}, J::Ideal{T}) where T <: RingElement
-   G1 = gens(J)
-   G2 = gens(I)
-   if isempty(G1)
-      return true
-   end
-   if isempty(G2)
-      return false
-   end
-   return divides(G1[1], G2[1])[1]
-end
-
-function Base.contains(I::Ideal{T}, J::Ideal{T}) where {U <: RingElement, T <: Union{AbstractAlgebra.PolyRingElem{U}, AbstractAlgebra.MPolyRingElem{U}}}
-   G = gens(J)
-   for v in G
-      if !iszero(normal_form(v, I))
-         return false
-      end
-   end
-   return true
+function Base.issubset(I::Ideal{T}, J::Ideal{T}) where T <: RingElement
+   return all(in(J), gens(I))
 end
 
 ###############################################################################
@@ -2177,9 +2159,9 @@ function intersect(I::Ideal{T}, J::Ideal{T}) where {U <: FieldElement, T <: Abst
 end
 
 function intersect(I::Ideal{T}, J::Ideal{T}) where {U <: RingElement, T <: AbstractAlgebra.PolyRingElem{U}}
-   if contains(I, J)
+   if is_subset(J, I)
       return J
-   elseif contains(J, I)
+   elseif is_subset(I, J)
       return I
    end
    S = base_ring(I) # poly ring
@@ -2200,9 +2182,9 @@ function intersect(I::Ideal{T}, J::Ideal{T}) where {U <: RingElement, T <: Abstr
 end
 
 function intersect(I::Ideal{T}, J::Ideal{T}) where {U <: RingElement, T <: AbstractAlgebra.MPolyRingElem{U}}
-   if contains(I, J)
+   if is_subset(J, I)
       return J
-   elseif contains(J, I)
+   elseif is_subset(I, J)
       return I
    end
    S = base_ring(I) # poly ring

test/generic/Ideal-test.jl

@@ -367,7 +367,7 @@ end
       I = Generic.Ideal(R, V)
       J = Generic.Ideal(R, vcat(V, W))
 
-      @test contains(J, I)
+      @test is_subset(I, J)
    end
 
    # univariate
@@ -382,7 +382,7 @@ end
       I = Generic.Ideal(R, V)
       J = Generic.Ideal(R, vcat(V, W))
 
-      @test contains(J, I)
+      @test is_subset(I, J)
    end
 
    # Fp[x]
@@ -398,7 +398,7 @@ end
       I = Generic.Ideal(R, V)
       J = Generic.Ideal(R, vcat(V, W))
 
-      @test contains(J, I)
+      @test is_subset(I, J)
    end
 
    # integer
@@ -411,13 +411,13 @@ end
       I = Generic.Ideal(ZZ, V)
       J = Generic.Ideal(ZZ, vcat(V, W))
 
-      @test contains(J, I)
+      @test is_subset(I, J)
    end
 
    I = Generic.Ideal(ZZ, 2)
 
-   @test contains(I, Generic.Ideal(ZZ, BigInt[]))
-   @test !contains(Generic.Ideal(ZZ, BigInt[]), I)
+   @test is_subset(Generic.Ideal(ZZ, BigInt[]), I)
+   @test !is_subset(I, Generic.Ideal(ZZ, BigInt[]))
 end
 
 @testset "Generic.Ideal.addition" begin
@@ -430,8 +430,8 @@ end
       I = Generic.Ideal(R, V)
       J = Generic.Ideal(R, W)
 
-      @test contains(I + J, I)
-      @test contains(I + J, J)
+      @test is_subset(I, I + J)
+      @test is_subset(J, I + J)
    end
 
    # univariate
@@ -446,8 +446,8 @@ end
       I = Generic.Ideal(R, V)
       J = Generic.Ideal(R, W)
 
-      @test contains(I + J, I)
-      @test contains(I + J, J)
+      @test is_subset(I, I + J)
+      @test is_subset(J, I + J)
    end
 
    # Fp[x]
@@ -463,8 +463,8 @@ end
       I = Generic.Ideal(R, V)
       J = Generic.Ideal(R, W)
 
-      @test contains(I + J, I)
-      @test contains(I + J, J)
+      @test is_subset(I, I + J)
+      @test is_subset(J, I + J)
    end
 
    # integer
@@ -477,8 +477,8 @@ end
       I = Generic.Ideal(ZZ, V)
       J = Generic.Ideal(ZZ, W)
 
-      @test contains(I + J, I)
-      @test contains(I + J, J)
+      @test is_subset(I, I + J)
+      @test is_subset(J, I + J)
    end
 end
 
@@ -627,8 +627,8 @@ end
 
       K = intersect(I, J)
 
-      @test contains(I, K)
-      @test contains(J, K)
+      @test is_subset(K, I)
+      @test is_subset(K, J)
    end
 
    # univariate
@@ -645,8 +645,8 @@ end
 
       K = intersect(I, J)
 
-      @test contains(I, K)
-      @test contains(J, K)
+      @test is_subset(K, I)
+      @test is_subset(K, J)
    end
 
    # Fp[x]
@@ -664,8 +664,8 @@ end
 
       K = intersect(I, J)
 
-      @test contains(I, K)
-      @test contains(J, K)
+      @test is_subset(K, I)
+      @test is_subset(K, J)
    end
 
    # integer
@@ -680,7 +680,7 @@ end
 
       K = intersect(I, J)
 
-      @test contains(I, K)
-      @test contains(J, K)
+      @test is_subset(K, I)
+      @test is_subset(K, J)
    end
 end