From b83975b04ffabd1b1d6e53e9bd05646678c92641 Mon Sep 17 00:00:00 2001
From: timholy <tim.holy@gmail.com>
Date: Sun, 6 Apr 2014 07:40:47 -0500
Subject: [PATCH] Add Cartesian product iteration. Fixes #1917

---
 base/exports.jl          |  1 +
 base/multidimensional.jl | 17 +++++++++++++++++
 test/combinatorics.jl    |  6 ++++++
 3 files changed, 24 insertions(+)

diff --git a/base/exports.jl b/base/exports.jl
index ab32dc26f1c5e..85cea3237e09c 100644
--- a/base/exports.jl
+++ b/base/exports.jl
@@ -918,6 +918,7 @@ export
 # iteration
     done,
     enumerate,
+    eachindex,
     next,
     start,
     zip,
diff --git a/base/multidimensional.jl b/base/multidimensional.jl
index 07e7df2470d77..fa65c6956e0b1 100644
--- a/base/multidimensional.jl
+++ b/base/multidimensional.jl
@@ -1,3 +1,20 @@
+# Cartesian product iteration
+
+immutable SizeIterator{N}
+    I::NTuple{N,Int}
+end
+getindex(I::SizeIterator, n) = I.I[n]
+
+@ngenerate N NTuple{N,Int} start{N}(lim::SizeIterator{N}) = @ntuple N d->1
+done{N}(lim::SizeIterator{N}, I::NTuple{N,Int}) = I[N] > lim[N]
+@ngenerate N (NTuple{N,Int},NTuple{N,Int}) function next{N}(lim::SizeIterator{N}, I::NTuple{N,Int})
+    @nif N i->I[i]<lim[i] i->(newI = @ntuple N d->((d < i)  ? 1 : ((d == i) ? I[d]+1 : I[d])))
+    I, newI
+end
+
+eachindex(A::Array) = SizeIterator(size(A))
+eachindex(dims::Dims) = SizeIterator(dims)
+
 ### From array.jl
 
 @ngenerate N Nothing function checksize(A::AbstractArray, I::NTuple{N, Any}...)
diff --git a/test/combinatorics.jl b/test/combinatorics.jl
index 49b9fac475d6f..44d596f7a57d5 100644
--- a/test/combinatorics.jl
+++ b/test/combinatorics.jl
@@ -34,3 +34,9 @@ end
 @test binomial(int64(67), int64(29)) == binomial(BigInt(67), BigInt(29)) == 7886597962249166160
 @test binomial(int128(131), int128(62)) == binomial(BigInt(131), BigInt(62)) == 157311720980559117816198361912717812000 
 
+# Cartesian product iteration
+A = reshape(1:6, 2, 3)
+indexes = ((1,1),(2,1),(1,2),(2,2),(1,3),(2,3))
+for (I,ind) in zip(eachindex(A), indexes)
+    @test I == ind
+end