It always helps to put a Debug.Trace.trace:<div><br></div><div> in if trace (show (fromEnum c)) $ c == ((!!) "ht" randInt) then p</div><div><br></div><div><div>What's your guess, heads or tails ('h' or 't')?</div>
<div>h</div><div>104</div><div>You win!</div><div>What's your guess, heads or tails ('h' or 't')?</div><div><b>10</b></div><div>You lose!</div><div>What's your guess, heads or tails ('h' or 't')?</div>
<div><br></div><div>So getChar also receives the linefeed character.</div><div><br></div><div>An easy way to get around this, is to use getLine instead and just use the first character, as in</div><div><br></div><div><div>
>> fmap head getLine </div><div><br></div><div>But of course we're hacking away here :-)<br></div><div><br></div></div><div class="gmail_quote">On Mon, Oct 12, 2009 at 12:10 AM, michael rice <span dir="ltr"><<a href="mailto:nowgate@yahoo.com">nowgate@yahoo.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><table cellspacing="0" cellpadding="0" border="0"><tbody><tr><td valign="top" style="font:inherit">What is going wrong here?<br>
<br>Michael<br><br>=======<br><br>import System.Random<br><br>coinToss :: StdGen -> IO ()<br>coinToss gen = putStrLn "What's your guess, heads or tails ('h' or 't')?"<br> >> getChar<br>
>>= \c -> let (randInt, _) = randomR(0,1) gen :: (Int, StdGen)<br> in if c == ((!!) "ht" randInt) then putStrLn "You win!" else putStrLn "You lose!"<br>
<br>main = do<br> gen <- getStdGen<br> coinToss gen<br> gen
<- newStdGen<br> main<br><br>=======<br><br>[michael@localhost ~]$ runhaskell cointoss.hs<br>What's your guess, heads or tails ('h' or 't')?<br>h<br>You win!<br>What's your guess, heads or tails ('h' or 't')?<br>
You lose!<br>What's your guess, heads or tails ('h' or 't')?<br>h<br>You lose!<br>What's your guess, heads or tails ('h' or 't')?<br>You lose!<br>What's your guess, heads or tails ('h' or 't')?<br>
^Ccointoss.hs: cointoss.hs: interrupted<br>[michael@localhost ~]$ <br><br></td></tr></tbody></table><br>
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<br></blockquote></div><br></div>