unary minus for toric divisors (#2697)

oscar-system · Aug 18, 2023 · adc6d9f · adc6d9f
1 parent 8e16945
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diff --git a/src/AlgebraicGeometry/ToricVarieties/ToricDivisorClasses/constructors.jl b/src/AlgebraicGeometry/ToricVarieties/ToricDivisorClasses/constructors.jl
@@ -95,6 +95,7 @@ function Base.:-(tdc1::ToricDivisorClass, tdc2::ToricDivisorClass)
     return toric_divisor_class(toric_variety(tdc1), divisor_class(tdc1) - divisor_class(tdc2))
 end
 
+Base.:-(td :: ToricDivisorClass) = toric_divisor_class(toric_variety(td), -divisor_class(td))
 
 Base.:*(c::T, tdc::ToricDivisorClass) where {T <: IntegerUnion} = toric_divisor_class(toric_variety(tdc), ZZRingElem(c) * divisor_class(tdc))
 

diff --git a/src/AlgebraicGeometry/ToricVarieties/ToricDivisorClasses/standard_constructions.jl b/src/AlgebraicGeometry/ToricVarieties/ToricDivisorClasses/standard_constructions.jl
@@ -33,7 +33,7 @@ julia> anticanonical_divisor_class(v)
 Divisor class on a normal toric variety
 ```
 """
-@attr ToricDivisorClass anticanonical_divisor_class(v::AbstractNormalToricVariety) = toric_divisor_class(anticanonical_divisor(v))
+@attr ToricDivisorClass anticanonical_divisor_class(v::AbstractNormalToricVariety) = -canonical_divisor_class(v)
 
 
 @doc raw"""

diff --git a/src/AlgebraicGeometry/ToricVarieties/ToricDivisors/constructors.jl b/src/AlgebraicGeometry/ToricVarieties/ToricDivisors/constructors.jl
@@ -94,6 +94,7 @@ function Base.:-(td1::ToricDivisor, td2::ToricDivisor)
     return toric_divisor(toric_variety(td1), new_coeffiicients)
 end
 
+Base.:-(td :: ToricDivisor) = toric_divisor(toric_variety(td), -coefficients(td))
 
 Base.:*(c::T, td::ToricDivisor) where {T <: IntegerUnion} = toric_divisor(toric_variety(td), [ZZRingElem(c)*x for x in coefficients(td)])
 

diff --git a/src/AlgebraicGeometry/ToricVarieties/ToricDivisors/standard_constructions.jl b/src/AlgebraicGeometry/ToricVarieties/ToricDivisors/standard_constructions.jl
@@ -33,7 +33,7 @@ julia> anticanonical_divisor(v)
 Torus-invariant, non-prime divisor on a normal toric variety
 ```
 """
-@attr ToricDivisor anticanonical_divisor(v::AbstractNormalToricVariety) = toric_divisor(v, fill(ZZRingElem(1), nrays(v)))
+@attr ToricDivisor anticanonical_divisor(v::AbstractNormalToricVariety) = -canonical_divisor(v)
 
 
 @doc raw"""