Fix single number (v/h)cat

src/derivatives/arrays.jl

@@ -58,17 +58,17 @@ end
 
 @grad function vcat(xs::Union{Number, AbstractVecOrMat}...)
     xs_value = value.(xs)
-    out_value = reduce(vcat,xs_value)
+    out_value = vcat(xs_value...,)
     function back(Δ)
         start = 0
         Δs = map(xs) do xsi
-          if xsi isa Number
-            d = Δ[start+1]
-          else
-            d = Δ[start+1:start+size(xsi,1), :]
-          end
-          start += size(xsi, 1)
-          d
+            if xsi isa Number
+                d = Δ[start+1]
+            else
+                d = Δ[start+1:start+size(xsi,1), :]
+            end
+            start += size(xsi, 1)
+            d
         end
         return (Δs...,)
     end
@@ -77,20 +77,20 @@ end
 
 @grad function hcat(xs::Union{Number, AbstractVecOrMat}...)
     xs_value = value.(xs)
-    out_value = reduce(hcat, xs_value)
+    out_value = hcat(xs_value...,)
     function back(Δ)
         start = 0
         Δs = map(xs) do xsi
-          d = if ndims(xsi) == 0
-            Δ[start+1]
-          elseif ndims(xsi) == 1
-            Δ[:, start+1]
-          else
-            i = map(_ -> :, size(xsi)) |> Base.tail |> Base.tail
-            Δ[:, start+1:start+size(xsi,2), i...]
-          end
-          start += size(xsi, 2)
-          d
+            d = if ndims(xsi) == 0
+                Δ[start+1]
+            elseif ndims(xsi) == 1
+                Δ[:, start+1]
+            else
+                i = map(_ -> :, size(xsi)) |> Base.tail |> Base.tail
+                Δ[:, start+1:start+size(xsi,2), i...]
+            end
+            start += size(xsi, 2)
+            d
         end
         return (Δs...,)
     end        
@@ -106,17 +106,17 @@ end
     return cat(Xs_value...; dims = dims), Δ -> begin
         start = ntuple(i -> 0, Val(ndims(Δ)))
         Δs = map(Xs) do xs
-          if xs isa Number
-            d = Δ[start+1]
-            start = start .+ 1
-          else
-            dim_xs = 1:ndims(xs)
-            till_xs = ntuple((i -> i in dims ? (i in dim_xs ? size(xs,i) : 1) : 0), Val(ndims(Δ)))
-            xs_in_Δ = ntuple(i -> till_xs[i] > 0 ? (start[i]+1:start[i]+till_xs[i]) : Colon(), Val(ndims(Δ)))
-            d = reshape(Δ[xs_in_Δ...],size(xs))
-            start = start .+ till_xs
-          end
-          d
+            if xs isa Number
+                d = Δ[start+1]
+                start = start .+ 1
+            else
+                dim_xs = 1:ndims(xs)
+                till_xs = ntuple((i -> i in dims ? (i in dim_xs ? size(xs,i) : 1) : 0), Val(ndims(Δ)))
+                xs_in_Δ = ntuple(i -> till_xs[i] > 0 ? (start[i]+1:start[i]+till_xs[i]) : Colon(), Val(ndims(Δ)))
+                d = reshape(Δ[xs_in_Δ...],size(xs))
+                start = start .+ till_xs
+            end
+            d
         end
         return (Δs...,)
     end

test/derivatives/ArrayFunctionTests.jl

@@ -16,18 +16,25 @@ end
     @test any(iszero, track([ones(2); 0.0]))
 end
 
-function testcat(f, args::Tuple{Any, Any}, type, kwargs=NamedTuple())
+function testcat(f, args::Tuple, type, kwargs=NamedTuple())
     x = f(track.(args)...; kwargs...)
     @test x isa type
     @test value(x) == f(args...; kwargs...)
 
-    x = f(track(args[1]), args[2]; kwargs...)
-    @test x isa type
-    @test value(x) == f(args...; kwargs...)
+    if length(args) == 1
+        x = f(track(args[1]); kwargs...)
+        @test x isa type
+        @test value(x) == f(args...; kwargs...)
+    else
+        @assert length(args) == 2
+        x = f(track(args[1]), args[2]; kwargs...)
+        @test x isa type
+        @test value(x) == f(args...; kwargs...)
 
-    x = f(args[1], track(args[2]); kwargs...)
-    @test x isa type
-    @test value(x) == f(args...; kwargs...)
+        x = f(args[1], track(args[2]); kwargs...)
+        @test x isa type
+        @test value(x) == f(args...; kwargs...)
+    end
 
     args = (args..., args...)
     x = f(track.(args)...; kwargs...)
@@ -64,6 +71,7 @@ end
     a = rand(3,3,3)
     n = rand()
 
+    testcat(cat, (n,), TrackedVector, (dims=1,))
     testcat(cat, (n, n), TrackedVector, (dims=1,))
     testcat(cat, (n, n), TrackedMatrix, (dims=2,))
     testcat(cat, (v, n), TrackedVector, (dims=1,))
@@ -79,11 +87,13 @@ end
     testcat(cat, (a, a), TrackedArray, (dims=3,))
     testcat(cat, (a, m), TrackedArray, (dims=3,))
 
+    testcat(vcat, (n,), TrackedVector)
     testcat(vcat, (n, n), TrackedVector)
     testcat(vcat, (v, n), TrackedVector)
     testcat(vcat, (n, v), TrackedVector)
     testcat(vcat, (v, v), TrackedVector)
 
+    testcat(hcat, (n,), TrackedMatrix)
     testcat(hcat, (n, n), TrackedMatrix)
     testcat(hcat, (v, v), TrackedMatrix)
     testcat(hcat, (v, m), TrackedMatrix)