batch data structure

src/Flux.jl

@@ -1,6 +1,7 @@
 module Flux
 
 using MacroTools, Lazy, Flow, Juno
+import Juno: Tree, Row
 
 # Zero Flux Given
 

src/batching.jl

@@ -1,8 +1,35 @@
 export batch
 
-# Treat the first dimension as the batch index
-# TODO: custom data type for this
+# TODO: support the Batch type only
 batch(x) = reshape(x, (1,size(x)...))
 batch(xs...) = vcat(map(batch, xs)...)
 
-unbatch(xs) = reshape(xs, size(xs)[2:end])
+type Batch{T,T′} <: AbstractVector{T}
+  data::T′
+end
+
+Base.size(b::Batch) = (size(b.data, 1),)
+
+Base.getindex(b::Batch, i) = slicedim(b.data, 1, i)::eltype(b)
+
+Base.setindex!(b::Batch, v, i) = b[i, :] = v
+
+function (::Type{Batch{T}}){T}(xs::T...)
+  length(xs) == 1 || @assert ==(map(size, xs)...)
+  batch = similar(xs[1], length(xs), size(xs[1])...)
+  for i = 1:length(xs)
+    batch[i, :] = xs[i]
+  end
+  return Batch{T,typeof(batch)}(batch)
+end
+
+function Batch(xs...)
+  xs′ = promote(xs...)
+  Batch{typeof(xs′[1])}(xs′...)
+end
+
+@render Juno.Inline b::Batch begin
+  Tree(Row(Text("Batch of "), eltype(b),
+           Juno.fade("[$(length(b))]")),
+           Juno.trim(collect(b)))
+end