Use state::Int for iterating over LinearFast AbstractArrays

This makes it easier to use integer offsets when iterating over a
subset of an AbstractVector.

base/abstractarray.jl

@@ -373,9 +373,16 @@ zero{T}(x::AbstractArray{T}) = fill!(similar(x), zero(T))
 # While the definitions for LinearFast are all simple enough to inline on their
 # own, LinearSlow's CartesianRange is more complicated and requires explicit
 # inlining.
-start(A::AbstractArray) = (@_inline_meta(); itr = eachindex(A); (itr, start(itr)))
-next(A::AbstractArray,i) = (@_inline_meta(); (idx, s) = next(i[1], i[2]); (A[idx], (i[1], s)))
-done(A::AbstractArray,i) = done(i[1], i[2])
+start(A::AbstractArray) = (@_inline_meta(); _start(linearindexing(A), A))
+_start(::LinearFast, A::AbstractArray) = 1
+_start(::LinearSlow, A::AbstractArray) = (@_inline_meta(); itr = eachindex(A); (itr, start(itr)))
+
+next(A::AbstractArray,i) = (@_inline_meta(); _next(A,i))
+_next(A::AbstractArray,i) = (@_inline_meta(); (idx, s) = next(i[1], i[2]); (A[idx], (i[1], s)))
+_next(A::AbstractArray,i::Int) = (A[i],i+1)
+done(A::AbstractArray,i) = (@_inline_meta(); _done(A, i))
+_done(A::AbstractArray,i) = done(i[1], i[2])
+_done(A::AbstractArray,i::Int) = i == length(A)+1
 
 # eachindex iterates over all indices. LinearSlow definitions are later.
 eachindex(A::AbstractArray) = (@_inline_meta(); eachindex(linearindexing(A), A))

base/array.jl

@@ -210,11 +210,6 @@ Return an array of all items in a collection. For associative collections, retur
 """
 collect(itr) = collect(eltype(itr), itr)
 
-## Iteration ##
-start(A::Array) = 1
-next(a::Array,i) = (a[i],i+1)
-done(a::Array,i) = i == length(a)+1
-
 ## Indexing: getindex ##
 
 # This is more complicated than it needs to be in order to get Win64 through bootstrap