Re: [Haskell-cafe] Simple program. Simple problem?

btw I always find it amusing to play with interact and lazy IO: guess :: [Char] -> [String] -> [String] guess (c:cs) ~(i:is) = "What's your guess, heads or tails ('h' or 't')?" : (if [c]==i then "You win!" else "You lose!") : guess cs is main = do gen <- getStdGen let rs = randomRs (0,1::Int) gen cs = map ("ht"!!) rs interact $ unlines . guess cs . lines On Mon, Oct 12, 2009 at 12:24 AM, Peter Verswyvelen wrote:

It always helps to put a Debug.Trace.trace: in if trace (show (fromEnum c)) $ c == ((!!) "ht" randInt) then p

What's your guess, heads or tails ('h' or 't')? h 104 You win! What's your guess, heads or tails ('h' or 't')? *10* You lose! What's your guess, heads or tails ('h' or 't')?

So getChar also receives the linefeed character.

An easy way to get around this, is to use getLine instead and just use the first character, as in

>> fmap head getLine

But of course we're hacking away here :-)

On Mon, Oct 12, 2009 at 12:10 AM, michael rice wrote:

...

What is going wrong here?

Michael

=======

import System.Random

coinToss :: StdGen -> IO () coinToss gen = putStrLn "What's your guess, heads or tails ('h' or 't')?" >> getChar >>= \c -> let (randInt, _) = randomR(0,1) gen :: (Int, StdGen) in if c == ((!!) "ht" randInt) then putStrLn "You win!" else putStrLn "You lose!"

main = do gen <- getStdGen coinToss gen gen <- newStdGen main

=======

[michael@localhost ~]$ runhaskell cointoss.hs What's your guess, heads or tails ('h' or 't')? h You win! What's your guess, heads or tails ('h' or 't')? You lose! What's your guess, heads or tails ('h' or 't')? h You lose! What's your guess, heads or tails ('h' or 't')? You lose! What's your guess, heads or tails ('h' or 't')? ^Ccointoss.hs: cointoss.hs: interrupted [michael@localhost ~]$

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