Add diff(::AbstractFill)

Author: dlfivefifty

src/FillArrays.jl

@@ -2,11 +2,9 @@ module FillArrays
 
 using LinearAlgebra, SparseArrays
 import Base: size, getindex, setindex!, IndexStyle, checkbounds, convert,
-    +, -, *, /, sum, cumsum, maximum, minimum, sort, sort!,
+    +, -, *, /, \, diff, sum, cumsum, maximum, minimum, sort, sort!,
     any, all, axes, isone, iterate, unique, allunique, permutedims, inv
 
-import Base.\
-
 import LinearAlgebra: rank, svdvals!, tril, triu, tril!, triu!, diag
 
 import Base.Broadcast: broadcasted, DefaultArrayStyle, broadcast_shape
@@ -379,6 +377,13 @@ cumsum(x::Ones{II}) where II<:Integer = Base.OneTo{II}(length(x))
 cumsum(x::Ones{Bool}) = Base.OneTo{Int}(length(x))
 cumsum(x::AbstractFill{Bool}) = cumsum(convert(AbstractFill{Int}, x))
 
+
+#########
+# Diff
+#########
+
+diff(x::AbstractFill{T,1}) where T = Zeros{T}(length(x)-1)
+
 #########
 # unique
 #########

test/runtests.jl

@@ -393,7 +393,7 @@ end
     @test sort(Ones(5)) == sort!(Ones(5))
 end
 
-@testset "Cumsum" begin
+@testset "Cumsum and diff" begin
     @test sum(Fill(3,10)) ≡ 30
     @test cumsum(Fill(3,10)) ≡ 3:3:30
 
@@ -412,6 +412,9 @@ end
     @test cumsum(Zeros{Bool}(10)) ≡ Zeros{Bool}(10)
     @test cumsum(Ones{Bool}(10)) ≡ Base.OneTo{Int}(10)
     @test cumsum(Fill(true,10)) ≡ 1:1:10
+
+    @test diff(Fill(1,10)) ≡ Zeros{Int}(9)
+    @test diff(Ones{Float64}(10)) ≡ Zeros{Float64}(9)
 end
 
 @testset "Broadcast" begin