2 Oct
2008
2 Oct
'08
2:20 p.m.
On Wed, Oct 1, 2008 at 7:53 PM, wren ng thornton
[1] Just like existential types, you can put something in but you can never get it back out again. For inescapable monads like IO and ST, this is why they have the behavior of sucking your whole program into the existential black-hole.
That's true for IO, but the whole point of ST is that it *is*
escapable. What makes ST (and IO and STM) unusual is that it can't be
implemented in pure Haskell without special support from the run-time
system.
--
Dave Menendez