On Oct 8, 2009, at 11:43 , michael rice wrote:
This doesn't:import System.Random main = do gen <- getStdGen let (randNumber, newGen) = randomR (1,6) gen :: (Int, StdGen) in putStrLn $ "Number is " ++ show randNumber [mich...@localhost ~]$ runhaskell zz.hs zz.hs:4:2: The last statement in a 'do' construct must be an expression
The problem here is that the "do" construct parses things a bit differently; if you're at the same indentation level, it inserts a (>>) on the assumption that the next line is an independent expression, so you need to indent the "in" a bit more to avoid it.
Note however that this usage is common enough that "do" provides a shorthand: you can simply omit the "in", and "let" will be parsed as if it were a statement:
> main = do > gen <- getStdGen > let (randNumber, newGen) = randomR (1,6) gen :: (Int,StdGen) > putStrLn $ "Number is " ++ show randNumber -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH
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