Implement equality between ExponentsIterator (#344)

Author: blegat

src/comparison.jl

@@ -481,6 +481,13 @@ function Base.IteratorSize(::Type{<:ExponentsIterator{M,Int}}) where {M}
     return Base.HasLength()
 end
 
+function Base.:(==)(a::ExponentsIterator, b::ExponentsIterator)
+    return typeof(a.object) == typeof(b.object) &&
+           length(a.object) == length(b.object) &&
+           a.mindegree == b.mindegree &&
+           a.maxdegree == b.maxdegree
+end
+
 function _length(it::ExponentsIterator, maxdegree)
     if maxdegree < it.mindegree
         return 0

test/comparison.jl

@@ -17,6 +17,15 @@ function _test(nvars::Int, M; kws...)
     return
 end
 
+function test_equal()
+    exp = ExponentsIterator{LexOrder}([0])
+    @test exp == ExponentsIterator{LexOrder}([0])
+    @test exp != ExponentsIterator{LexOrder}((0,))
+    @test exp != ExponentsIterator{LexOrder}([0, 0])
+    @test exp != ExponentsIterator{LexOrder}([0], mindegree = 1)
+    @test exp != ExponentsIterator{LexOrder}([0], maxdegree = 2)
+end
+
 function test_errors()
     err = ArgumentError(
         "The `mindegree` of `ExponentsIterator` cannot be negative.",