Infinite loop with showFlow

[mpickering]

Using showFlow on a flow which uses mapA causes an unproductive infinite loop.

showFlow (mapA (arr (+1)))
> "....(unproductive loop)

[bgamari]

The problem here is that mapA results in an infinite tree of choice nodes since we don't statically know the size of the structure being mapped over.

[dorranh]

This is still an interesting point and should be considered when implementing showFlow for funflow 2.