Excerpts from wren ng thornton's message of Thu Nov 12 08:17:41 +0100 2009:
Nicolas Pouillard wrote:
Excerpts from jean-christophe mincke's message of Tue Nov 10 21:18:34 +0100 2009:
do acc <- get put (acc+1) ...
Since this pattern occurs often 'modify' is a combination of get and put:
do modify (+1) ...
Though the caveat about laziness applies here as well. modify is famously lazy which can lead to space leaks and stack overflows. Better would be to define and use your own strict version:
modify' f = get >>= \x -> put $! f x
However if you want a strict state you should better use Control.Monad.State.Strict [1]. Finally I'm wondering if [1] is strict enough... [1]: http://www.haskell.org/ghc/docs/latest/html/libraries/mtl/Control-Monad-Stat... -- Nicolas Pouillard http://nicolaspouillard.fr