fix: isless broken for mixed types (#73)

Fixes #72.

Author: briochemc

src/dual.jl

@@ -171,7 +171,7 @@ Base.isequal(z::Dual, w::Dual) = isequal(value(z),value(w)) && isequal(epsilon(z
 Base.isequal(z::Dual, x::Number) = isequal(value(z), x) && isequal(epsilon(z), zero(x))
 Base.isequal(x::Number, z::Dual) = isequal(z, x)
 
-Base.isless(z::Dual{T},w::Dual{T}) where {T<:Real} = value(z) < value(w)
+Base.isless(z::Dual{<:Real},w::Dual{<:Real}) = value(z) < value(w)
 Base.isless(z::Real,w::Dual{<:Real}) = z < value(w)
 Base.isless(z::Dual{<:Real},w::Real) = value(z) < w
 

test/automatic_differentiation_test.jl

@@ -20,6 +20,8 @@ y = sin(x)+exp(x)
 @test epsilon(y) ≈ cos(2)+exp(2)
 
 @test x > 1
+@test dual(1) < dual(2.0)
+@test dual(1.0) < dual(2.0)
 y = abs(-x)
 @test value(y) ≈ 2.0
 @test epsilon(y) ≈ 1.0