Checks for zeroness (#332)

* Checks for zeroness

* Remove iszero equality checks

* Add tests for iszero

Author: projekter

src/rewrite.jl

@@ -79,6 +79,9 @@ function Base.:/(z::Zero, x::Any)
     end
 end
 
+Base.iszero(::Zero) = true
+Base.isone(::Zero) = false
+
 # These methods are used to provide an efficient implementation for the common
 # case like `x^2 * sum(f for i in 1:0)`, which lowers to
 # `_MA.operate!!(*, x^2, _MA.Zero())`. We don't need the method with reversed

test/rewrite.jl

@@ -19,6 +19,8 @@ import MutableArithmetics as MA
     @test -z isa MA.Zero
     @test +z isa MA.Zero
     @test *(z) isa MA.Zero
+    @test iszero(z)
+    @test !isone(z)
 end
 
 # Test that the macro call `m` throws an error exception during pre-compilation