This package provides imperative-style loops supporting "continue" and
"break". For example:
import Control.Monad
import Control.Monad.IO.Class
import Control.Monad.Trans.Loop
import Control.Monad.Trans.Class
main :: IO ()
main =
foreach [0..] $ \i ->
foreach [0..] $ \j -> do
when (j == 0) $
continue -- skip to next iteration
when (j >= 5) $
exit -- exit the loop
when (i >= 5) $
lift exit -- exit the outer loop by calling 'exit'
in the parent monad
liftIO $ print (i, j)
It works by having the loop body run under the LoopT monad
transformer, which provides early exit functions 'continue' and
'exit'. Functions like 'foreach' and 'while' run a LoopT callback,
passing it continuations defining 'continue' and 'exit'.
http://hackage.haskell.org/package/control-monad-loop
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