zip'

src/tangent_types/abstract_zero.jl

@@ -81,7 +81,11 @@ function _promote_vectors(x::AbstractVector, y::AbstractVector)
  if isconcretetype(T)
  return convert(T, x), convert(T, y)
  else
- short = map(Base.splat(first ∘ promote), zip(x, y))
+ if VERSION > v"1.4"
+ short = map(first ∘ promote, x, y)
+ else # on 1.0 and friends, neither map nor zip stop early. So we improvise
+ short = [promote(x[i], y[i])[1] for i in intersect(axes(x, 1), axes(y, 1))]
+ end
  return convert(typeof(short), x), convert(typeof(short), y)
  end
 end