Implement Iteration interface and Indexing interface for 'SequentialT…

…ransform' (#6)

src/sequential.jl

@@ -68,6 +68,15 @@ Create a [`SequentialTransform`](@ref) transform with
 AbstractTrees.nodevalue(::SequentialTransform) = SequentialTransform
 AbstractTrees.children(s::SequentialTransform) = s.transforms
 
+# iteration interface
+Base.length(s::SequentialTransform) = length(s.transforms)
+Base.iterate(s::SequentialTransform, args...) = iterate(s.transforms, args...)
+
+# indexing interface
+Base.getindex(s::SequentialTransform, i) = getindex(s.transforms, i)
+Base.firstindex(s::SequentialTransform) = firstindex(s.transforms)
+Base.lastindex(s::SequentialTransform) = lastindex(s.transforms)
+
 Base.show(io::IO, s::SequentialTransform) = print(io, join(s.transforms, " → "))
 
 function Base.show(io::IO, ::MIME"text/plain", s::SequentialTransform)

test/runtests.jl

@@ -26,4 +26,21 @@ using Test
   T = TestTransform() → TestTransform()
   @test (T → Identity()) == T
   @test (Identity() → T) == T
+
+  # sequential
+  T = TransformsBase.SequentialTransform([TestTransform(), Identity()])
+  # iteration interface
+  @test length(T) == 2
+  T1, state = iterate(T)
+  @test T1 == TestTransform()
+  T2, state = iterate(T, state)
+  @test T2 == Identity()
+  @test isnothing(iterate(T, state))
+  # indexing interface
+  @test T[1] == TestTransform()
+  @test T[2] == Identity()
+  @test firstindex(T) == 1
+  @test lastindex(T) == 2
+  @test T[begin] == TestTransform()
+  @test T[end] == Identity()
 end