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 <bugfact@gmail.com> 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 <nowgate@yahoo.com> 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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