[Haskell-cafe] Documenting strictness properties for Data.Map.Strict

[Evan Laforge]

> Any ideas for further improvements?

I feel like there should be a canonical "what is WHNF" page on
haskell.org that docs like this can link to.  Namely, what it is
theoretically, what that means for various examples of thunks (i.e.
show how a sample graph would get reduced), and what that means for
programs (e.g. this builds up thunks, this doesn't).

All this info is certainly available, but it seems to not be as easy
as it should be to find, e.g.
http://haskell.org/haskellwiki/Lazy_vs._non-strict says "described
WHNF..." and, well,
http://en.wikibooks.org/wiki/Haskell/Laziness#Thunks_and_Weak_head_normal_form
is pretty good actually.  Maybe the haskellwiki page should just link
to that.