Implement pairs like PR 22907 (#428)

Author: iamed2

README.md

@@ -201,6 +201,8 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * `IOContext` accepting key-value `Pair`s ([#23271]).
 
+* `pairs` for iterating over key-value `Pair`s ([#22907]).
+
 * `get` do-block syntax supported when using `ENV` ([#23412]).
 
 ## Renaming
@@ -368,6 +370,7 @@ includes this fix. Find the minimum version from there.
 [#22751]: https://github.com/JuliaLang/julia/issues/22751
 [#22761]: https://github.com/JuliaLang/julia/issues/22761
 [#22864]: https://github.com/JuliaLang/julia/issues/22864
+[#22907]: https://github.com/JuliaLang/julia/issues/22907
 [#23051]: https://github.com/JuliaLang/julia/issues/23051
 [#23235]: https://github.com/JuliaLang/julia/issues/23235
 [#23271]: https://github.com/JuliaLang/julia/issues/23271

src/Compat.jl

@@ -673,6 +673,51 @@ end
     export partialsort, partialsort!, partialsortperm, partialsortperm!
 end
 
+# 0.7.0-DEV.1660
+@static if !isdefined(Base, :pairs)
+    pairs(collection) = Base.Generator(=>, keys(collection), values(collection))
+    pairs(a::Associative) = a
+
+    # 0.6.0-dev+2834
+    @static if !isdefined(Iterators, :IndexValue)
+        include_string(@__MODULE__, """
+            immutable IndexValue{I,A<:AbstractArray}
+                data::A
+                itr::I
+            end
+        """)
+
+        Base.length(v::IndexValue)  = length(v.itr)
+        Base.indices(v::IndexValue) = indices(v.itr)
+        Base.size(v::IndexValue)    = size(v.itr)
+        @inline Base.start(v::IndexValue) = start(v.itr)
+        Base.@propagate_inbounds function Base.next(v::IndexValue, state)
+            indx, n = next(v.itr, state)
+            item = v.data[indx]
+            (indx => item), n
+        end
+        @inline Base.done(v::IndexValue, state) = done(v.itr, state)
+
+        Base.eltype{I,A}(::Type{IndexValue{I,A}}) = Pair{eltype(I), eltype(A)}
+
+        Base.iteratorsize{I}(::Type{IndexValue{I}}) = iteratorsize(I)
+        Base.iteratoreltype{I}(::Type{IndexValue{I}}) = iteratoreltype(I)
+
+        Base.reverse(v::IndexValue) = IndexValue(v.data, reverse(v.itr))
+    else
+        const IndexValue = Iterators.IndexValue
+    end
+
+    pairs(::IndexLinear,    A::AbstractArray) = IndexValue(A, linearindices(A))
+    pairs(::IndexCartesian, A::AbstractArray) = IndexValue(A, CartesianRange(indices(A)))
+
+    Base.keys(a::AbstractArray) = CartesianRange(indices(a))
+    Base.keys(a::AbstractVector) = linearindices(a)
+    Base.keys(s::IndexStyle, A::AbstractArray, B::AbstractArray...) = eachindex(s, A, B...)
+
+    Base.values(itr) = itr
+end
+
 # 0.7.0-DEV.1721
 @static if !isdefined(Base, :AbstractRange)
     const AbstractRange = Range

test/runtests.jl

@@ -741,6 +741,34 @@ let x = fill!(StringVector(5), 0x61)
     @test pointer(x) == pointer(String(x))
 end
 
+# PR 22907
+using Compat: pairs
+
+# keys, values, pairs
+for A in (rand(2), rand(2,3))
+    local A
+    for (i, v) in pairs(A)
+        @test A[i] == v
+    end
+    @test collect(values(A)) == collect(A)
+end
+
+let A = Dict(:foo=>1, :bar=>3)
+    for (k, v) in pairs(A)
+        @test A[k] == v
+    end
+    @test sort!(collect(pairs(A))) == sort!(collect(A))
+end
+
+let
+    A14 = [11 13; 12 14]
+    R = CartesianRange(indices(A14))
+    @test [a for (a,b) in pairs(IndexLinear(),    A14)] == [1,2,3,4]
+    @test [a for (a,b) in pairs(IndexCartesian(), A14)] == vec(collect(R))
+    @test [b for (a,b) in pairs(IndexLinear(),    A14)] == [11,12,13,14]
+    @test [b for (a,b) in pairs(IndexCartesian(), A14)] == [11,12,13,14]
+end
+
 # Val(x)
 # 0.7
 begin