Add diff (#136)

* Add diff

* Update test_splines.jl

* Update test_splines.jl

* Update test_splines.jl

Author: dlfivefifty

src/operators.jl

@@ -125,6 +125,14 @@ function diff(d::AbstractQuasiVector)
     Derivative(x)*d
 end
 
+function diff(A::AbstractQuasiArray; dims::Integer)
+    if dims == 1
+        Derivative(axes(A,1)) * A
+    else
+        error("Not implemented")
+    end
+end
+
 ^(D::Derivative, k::Integer) = ApplyQuasiArray(^, D, k)
 
 

test/test_splines.jl

@@ -158,6 +158,8 @@ import ContinuumArrays: basis, AdjointBasisLayout, ExpansionLayout, BasisLayout,
         @test D*L isa MulQuasiMatrix
         @test length((D*L).args) == 2
         @test eltype(D*L) == Float64
+        @test typeof(diff(L; dims=1)) == typeof(D*L)
+        @test_throws ErrorException diff(L; dims=2)
 
         M = applied(*, (D*L).args..., [1,2,4])
         @test eltype(materialize(M)) == Float64