2 Jul
2011
2 Jul
'11
3:25 p.m.
On Jul 2, 2011, at 11:04 AM, Brandon Allbery wrote:
The type tells you this right out, by the way:
undefined :: a
What can you do with a "value" that can be any conceivable type, and about which nothing else can be said? It has no handles, no behavior; the only possible interpretation is that it's not a value at all.
Its type makes undefined valuable in creating polymorphic functions. You can see many examples of it in my article for the Monad.Reader: "How to refold a map."
"undefined" is rendered by the symbol for "bottom" in the formatted code. ____________________ David Place Owner, Panpipes Ho! LLC http://panpipesho.com d@vidplace.com