Int(::Dual) and Integer(::Dual) (#508)

Author: dlfivefifty

Project.toml

@@ -1,6 +1,6 @@
 name = "ForwardDiff"
 uuid = "f6369f11-7733-5829-9624-2563aa707210"
-version = "0.10.18"
+version = "0.10.19"
 
 [deps]
 CommonSubexpressions = "bbf7d656-a473-5ed7-a52c-81e309532950"

src/dual.jl

@@ -305,6 +305,15 @@ end
 @inline Base.one(d::Dual) = one(typeof(d))
 @inline Base.one(::Type{Dual{T,V,N}}) where {T,V,N} = Dual{T}(one(V), zero(Partials{N,V}))
 
+@inline function Base.Int(d::Dual)
+    all(iszero, partials(d)) || throw(InexactError(:Int, Int, d))
+    Int(value(d))
+end
+@inline function Base.Integer(d::Dual)
+    all(iszero, partials(d)) || throw(InexactError(:Integer, Integer, d))
+    Integer(value(d))
+end
+
 @inline Random.rand(rng::AbstractRNG, d::Dual) = rand(rng, value(d))
 @inline Random.rand(::Type{Dual{T,V,N}}) where {T,V,N} = Dual{T}(rand(V), zero(Partials{N,V}))
 @inline Random.rand(rng::AbstractRNG, ::Type{Dual{T,V,N}}) where {T,V,N} = Dual{T}(rand(rng, V), zero(Partials{N,V}))

test/DualTest.jl

@@ -505,6 +505,19 @@ end
     @test !isfinite(dinf)
 end
 
+@testset "Integer" begin
+    x = Dual(1.0,0)
+    @test Int(x) ≡ Integer(x) ≡ convert(Int,x) ≡ convert(Integer,x) ≡ 1
+    x = Dual(1.0,0,0)
+    @test Int(x) ≡ Integer(x) ≡ convert(Int,x) ≡ convert(Integer,x) ≡ 1
+    @test_throws InexactError Int(Dual(1.5,1.2))
+    @test_throws InexactError Integer(Dual(1.5,1.2))
+    @test_throws InexactError Int(Dual(1,1))
+    @test_throws InexactError Integer(Dual(1,1,2))
+    @test length(UnitRange(Dual(1.5), Dual(3.5))) == 3
+    @test length(UnitRange(Dual(1.5,1), Dual(3.5,3))) == 3
+end
+  
 if VERSION >= v"1.6.0-rc1"
     @testset "@printf" begin
         for T in (Float16, Float32, Float64, BigFloat)