equality of derivatives (#169)

* equality of derivatives

* don't test for normalized spaces

Author: jishnub

src/Operators/banded/CalculusOperator.jl

@@ -229,6 +229,8 @@ for TYP in (:Derivative,:Integral,:Laplacian)
     end
 end
 
+==(A::Derivative, B::Derivative) = A.order == B.order && domainspace(A) == domainspace(B)
+
 
 """
 `Derivative(sp::Space,k::Int)` represents the `k`-th derivative on `sp`.

test/SpacesTest.jl

@@ -309,5 +309,18 @@ using StaticArrays
             g = Fun(Chebyshev(), [1,2,3])
             @test coefficients(f^2) == coefficients(g^2)
         end
+
+        @testset "Derivative" begin
+            @test Derivative() == Derivative()
+            for d in Any[(), (0..1,)]
+                for ST in Any[Chebyshev, Legendre]
+                    S = ST(d...)
+                    @test Derivative(S) == Derivative(S)
+                    @test Derivative(S,2) == Derivative(S,2)
+                end
+            end
+            @test Derivative(Chebyshev()) != Derivative(Chebyshev(), 2)
+            @test Derivative(Chebyshev()) != Derivative(Legendre())
+        end
     end
 end