On 20/10/09 20:32, Michael Mossey wrote:
Okay, I figured this out. mapM is not lazy, at least not for a monad that has state and under the circumstance you demand the state out the other side.
If I understand what you are saying then this behaviour isn't unexpected. If you have a monad with state, and you ask for the final state, then it's likely that everything happening in that particular monad will has to be evaluated.
I may rewrite the program. Or I may consider the ISS principle. ("Increase the stack, stupid.")
You may also be able to improve the situation by adding a bit of strictness. In some cases the thunks resulting from laziness can take up a lot of space. Forcing evaluation, at well thought out locations in your program, may both speed things up and reduce memory/stack usage. /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe