remove diff code for now

src/Flux.jl

@@ -13,7 +13,6 @@ include("model.jl")
 include("utils.jl")
 include("data.jl")
 
-include("compiler/diff.jl")
 include("compiler/code.jl")
 include("compiler/loops.jl")
 include("compiler/interp.jl")

src/compiler/diff.jl

@@ -1,30 +0,0 @@
-addΔ(a, b) = vertex(:+, a, b)
-
-# Special case a couple of operators to clean up output code
-const symbolic = Dict()
-
-symbolic[:+] = (Δ, args...) -> map(_->Δ, args)
-
-function ∇v(v::Vertex, Δ)
-  haskey(symbolic, value(v)) && return symbolic[value(v)](Δ, inputs(v)...)
-  Δ = vertex(:back!, constant(value(v)), constant(Δ), inputs(v)...)
-  map(i -> @flow(getindex($Δ, $i)), 1:DataFlow.nin(v))
-end
-
-function invert(v::IVertex, Δ = :Δ, out = d())
-  @assert !iscyclic(v)
-  if isconstant(v)
-    @assert !haskey(out, value(v))
-    out[value(v).value] = constant(Δ)
-  else
-    Δ′s = ∇v(v, Δ)
-    for (v′, Δ′) in zip(inputs(v), Δ′s)
-      invert(v′, Δ′, out)
-    end
-  end
-  return out
-end
-
-back!(::typeof(+), Δ, args...) = map(_ -> Δ, args)
-
-back!(::typeof(*), Δ, a, b) = Δ*b', a'*Δ