Data.IntMap.Strict.findWithDefault is too strict

[Edward Z. Yang]

Excerpts from Johan Tibell's message of Mon Dec 17 05:17:22 +0800 2012:
> We still need a clear policy how to handle these kind of function and
> other functions that don't directly insert things into maps (e.g.
> folds).

Strictness of accumulators is something of an orthogonal issue to
strictness of the maps; i.e. a strict fold can be useful for both
strict and lazy maps.

Cheers,
Edward