fmap package:backprop

Lifted fmap. Lifts backpropagatable functions to be backpropagatable functions on Traversable Functors.
fmap, but taking explicit add and zero.
fmap, but with Num constraints instead of Backprop constraints.
Efficient version of fmap when used to "replace" all values in a Functor value.
fmapConst x = fmap (const x)
but much more efficient.
fmapConst, but taking explicit add and zero.
fmapConst, but with Num constraints instead of Backprop constraints.