Added eachrow/col/slice for v1.0 (#658)

* Added eachrow/col/slice for v1.0

Author: jiegillet

README.md

@@ -114,6 +114,9 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 ## New functions, macros, and methods
 
+* `eachrow`, `eachcol`, and `eachslice` to iterate over first, second, or given dimension
+  of an array ([#29749]).
+
 * `isnothing` for testing if a variable is equal to `nothing` ([#29674]).
 
 * `Compat.readline` with `keep` keyword argument ([#25646])
@@ -570,3 +573,4 @@ includes this fix. Find the minimum version from there.
 [#28850]: https://github.com/JuliaLang/julia/issues/28850
 [#29259]: https://github.com/JuliaLang/julia/issues/29259
 [#29674]: https://github.com/JuliaLang/julia/issues/29674
+[#29749]: https://github.com/JuliaLang/julia/issues/29749

src/Compat.jl

@@ -931,6 +931,21 @@ if VERSION < v"1.1.0-DEV.472"
     isnothing(::Nothing) = true
 end
 
+# https://github.com/JuliaLang/julia/pull/29749
+@static if v"0.7" <= VERSION < v"1.1.0-DEV.792"
+    export eachrow, eachcol, eachslice
+    eachrow(A::AbstractVecOrMat) = (view(A, i, :) for i in axes(A, 1))
+    eachcol(A::AbstractVecOrMat) = (view(A, :, i) for i in axes(A, 2))
+    @inline function eachslice(A::AbstractArray; dims)
+        length(dims) == 1 || throw(ArgumentError("only single dimensions are supported"))
+        dim = first(dims)
+        dim <= ndims(A) || throw(DimensionMismatch("A doesn't have $dim dimensions"))
+        idx1, idx2 = ntuple(d->(:), dim-1), ntuple(d->(:), ndims(A)-dim)
+        return (view(A, idx1..., i, idx2...) for i in axes(A, dim))
+    end
+end
+
+
 
 @static if !isdefined(Base, :Some)
     import Base: promote_rule, convert

test/runtests.jl

@@ -30,6 +30,23 @@ end
 @test !isnothing(1)
 @test isnothing(nothing)
 
+# https://github.com/JuliaLang/julia/pull/29749
+if VERSION >= v"0.7"
+    @testset "row/column/slice iterators" begin
+        # Simple ones
+        M = [1 2 3; 4 5 6; 7 8 9]
+        @test collect(eachrow(M)) == collect(eachslice(M, dims = 1)) == [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
+        @test collect(eachcol(M)) == collect(eachslice(M, dims = 2)) == [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
+        @test_throws DimensionMismatch eachslice(M, dims = 4)
+        
+        # Higher-dimensional case
+        M = reshape([(1:16)...], 2, 2, 2, 2)
+        @test_throws MethodError collect(eachrow(M))
+        @test_throws MethodError collect(eachcol(M))
+        @test collect(eachslice(M, dims = 1))[1][:, :, 1] == [1 5; 3 7]
+    end
+end
+
 # julia#26365
 @test Compat.tr([1 2; 3 5]) == 6