From 0b374fbde031bd1195b0128257bdecf3f2a56ea0 Mon Sep 17 00:00:00 2001
From: Sacha Verweij <sacha@stanford.edu>
Date: Thu, 28 Jul 2016 16:03:54 -0700
Subject: [PATCH] Make `hvcat`s of heterogeneous combinations of dense matrices
 and vectors yield dense arrays (fixes #17686).

---
 base/array.jl    |  8 +++++---
 test/arrayops.jl | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/base/array.jl b/base/array.jl
index 4fc67b12ba356..89bec1acb5ee9 100644
--- a/base/array.jl
+++ b/base/array.jl
@@ -689,7 +689,6 @@ vcat{T}(A::Matrix{T}...) = typed_vcat(T, A...)
 hcat(A::Union{Matrix, Vector}...) = typed_hcat(promote_eltype(A...), A...)
 hcat{T}(A::Union{Matrix{T}, Vector{T}}...) = typed_hcat(T, A...)
 
-
 vcat(A::Union{Matrix, Vector}...) = typed_vcat(promote_eltype(A...), A...)
 vcat{T}(A::Union{Matrix{T}, Vector{T}}...) = typed_vcat(T, A...)
 
@@ -699,8 +698,11 @@ hvcat{T}(rows::Tuple{Vararg{Int}}, xs::Vector{T}...) = typed_hvcat(T, rows, xs..
 hvcat(rows::Tuple{Vararg{Int}}, xs::Matrix...) = typed_hvcat(promote_eltype(xs...), rows, xs...)
 hvcat{T}(rows::Tuple{Vararg{Int}}, xs::Matrix{T}...) = typed_hvcat(T, rows, xs...)
 
-cat(catdims, xs::Union{Matrix,Vector}...) = Base.cat_t(catdims, promote_eltype(xs...), xs...)
-cat{T}(catdims, xs::Union{Matrix{T},Vector{T}}...) = Base.cat_t(catdims, T, xs...)
+hvcat(rows::Tuple{Vararg{Int}}, xs::Union{Vector,Matrix}...) = typed_hvcat(promote_eltype(xs...), rows, xs...)
+hvcat{T}(rows::Tuple{Vararg{Int}}, xs::Union{Vector{T},Matrix{T}}...) = typed_hvcat(T, rows, xs...)
+
+cat(catdims, xs::Union{Vector,Matrix}...) = Base.cat_t(catdims, promote_eltype(xs...), xs...)
+cat{T}(catdims, xs::Union{Vector{T},Matrix{T}}...) = Base.cat_t(catdims, T, xs...)
 
 ## find ##
 
diff --git a/test/arrayops.jl b/test/arrayops.jl
index 60cd54e437f50..92549881f665b 100644
--- a/test/arrayops.jl
+++ b/test/arrayops.jl
@@ -1703,3 +1703,25 @@ for op in (:.+, :.*, :.÷, :.%, :.<<, :.>>, :.-, :./, :.\, :.//, :.^)
 end
 
 end
+
+# Test that concatenations of dense matrices/vectors yield dense matrices/vectors
+let
+    N = 4
+    densevec = ones(N)
+    densemat = diagm(ones(N))
+    # Test that concatenations of homogeneous pairs of either dense matrices or dense vectors
+    # (i.e., Matrix-Matrix concatenations, and Vector-Vector concatenations) yield dense arrays
+    for densearray in (densevec, densemat)
+        @test isa(vcat(densearray, densearray), Array)
+        @test isa(hcat(densearray, densearray), Array)
+        @test isa(hvcat((2,), densearray, densearray), Array)
+        @test isa(cat((1,2), densearray, densearray), Array)
+    end
+    # Test that concatenations of heterogeneous Matrix-Vector pairs yield dense matrices
+    @test isa(hcat(densemat, densevec), Array)
+    @test isa(hcat(densevec, densemat), Array)
+    @test isa(hvcat((2,), densemat, densevec), Array)
+    @test isa(hvcat((2,), densevec, densemat), Array)
+    @test isa(cat((1,2), densemat, densevec), Array)
+    @test isa(cat((1,2), densevec, densemat), Array)
+end