add linear indexing with single multi-dimensional index. closes #2247

Author: JeffBezanson

base/abstractarray.jl

@@ -465,6 +465,15 @@ end
 
 getindex(t::AbstractArray, i::Real) = error("indexing not defined for ", typeof(t))
 
+# linear indexing with a single multi-dimensional index
+function getindex(A::AbstractArray, I::AbstractArray)
+    x = similar(A, size(I))
+    for i=1:length(I)
+        x[i] = A[I[i]]
+    end
+    return x
+end
+
 # index A[:,:,...,i,:,:,...] where "i" is in dimension "d"
 # TODO: more optimized special cases
 slicedim(A::AbstractArray, d::Integer, i) =

base/array.jl

@@ -327,7 +327,7 @@ end
 # Multidimensional indexing
 let getindex_cache = nothing
 global getindex
-function getindex(A::Array, I::Union(Real,AbstractArray)...)
+function getindex(A::Array, I::Union(Real,AbstractVector)...)
     check_bounds(A, I...)
     I = indices(I)
     X = similar(A, index_shape(I...))

base/bitarray.jl

@@ -372,7 +372,7 @@ end
 
 let getindex_cache = nothing
     global getindex
-    function getindex(B::BitArray, I::Union(Real,AbstractArray)...)
+    function getindex(B::BitArray, I::Union(Real,AbstractVector)...)
         I = indices(I)
         X = BitArray(index_shape(I...))
         Xc = X.chunks

base/subarray.jl

@@ -244,7 +244,7 @@ function parentdims(s::SubArray)
     dimindex
 end
 
-function getindex(s::SubArray, I::Union(Real,AbstractArray)...)
+function getindex(s::SubArray, I::Union(Real,AbstractVector)...)
     newindexes = translate_indexes(s, I...)
 
     rs = index_shape(I...)

test/arrayops.jl

@@ -387,3 +387,14 @@ begin
         @test vec(S[i,:]) == sort(vec(a[i,:]))
     end
 end
+
+# single multidimensional index
+let
+    a = rand(6,6)
+    I = [1 4 5; 4 2 6; 5 6 3]
+    a2 = a[I]
+    @test size(a2) == size(I)
+    for i = 1:length(a2)
+        @test a2[i] == a[I[i]]
+    end
+end