If you are running from GHCi, just type run 100 at the prompt..<br><br>If you intend to compile it, you have to add<br><br>main = print $ run 100<br><br>The compiler adds a call to main::IO (), which is intended to be the main entry point of your code. <br>
<br>We need to add print, as run has type <br><br>run::Int-&gt;[Door]<br><br>so run 100 has type [Door].<br><br>print is <br><br>print::(Show a) =&gt; a -&gt; IO ()<br><br>The IO () stands for an empty IO monad, which is the black magic of haskell, intended to separate pure code from I/O side-effects... <br>
<br><br><br><br><div class="gmail_quote">On Mon, May 3, 2010 at 06:31, Samuel Williams <span dir="ltr">&lt;<a href="mailto:space.ship.traveller@gmail.com">space.ship.traveller@gmail.com</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div style="word-wrap: break-word;">Also, one more thing - if someone could write some comments to go along with the source code that explain what it is doing, that would be really helpful. I can see the general structure, but I don&#39;t know the ins and outs of Haskell. If someone could augment the example with comments explaining what the functions do that would be great!<div>
<br></div><div><div style="margin: 0px; line-height: 18px; color: rgb(51, 50, 153);">data <span style="color: rgb(19, 153, 17);"><b>Door</b></span> <span style="color: rgb(204, 1, 0);">=</span> <span style="color: rgb(19, 153, 17);"><b>Open</b></span> <span style="color: rgb(204, 1, 0);">|</span> <span style="color: rgb(19, 153, 17);"><b>Closed</b></span> deriving <span style="color: rgb(19, 153, 17);"><b>Show</b></span></div>
<p style="margin: 0px; font: 13px Menlo; color: rgb(51, 50, 153);"> </p><div style="margin: 0px; line-height: 18px; color: rgb(51, 50, 153);">toggle <span style="color: rgb(19, 153, 17);"><b>Open</b></span>   <span style="color: rgb(204, 1, 0);">=</span> <span style="color: rgb(19, 153, 17);"><b>Closed</b></span></div>
<div style="margin: 0px; line-height: 18px; color: rgb(19, 153, 17);"><span style="color: rgb(51, 50, 153);">toggle </span><b>Closed</b><span style="color: rgb(51, 50, 153);"> </span><span style="color: rgb(204, 1, 0);">=</span><span style="color: rgb(51, 50, 153);"> </span><b>Open</b></div>
<p style="margin: 0px; font: 13px Menlo; color: rgb(51, 50, 153);"> </p><div style="margin: 0px; line-height: 18px; color: rgb(51, 50, 153);">pass k <span style="color: rgb(204, 1, 0);">=</span> <span style="text-decoration: underline; color: rgb(58, 50, 255);">zipWith</span> ($) (cycle $ replicate k <span style="color: rgb(19, 153, 17);"><b>id</b></span> <span style="color: rgb(204, 1, 0);">++</span> <span style="color: rgb(204, 1, 0);">[</span>toggle<span style="color: rgb(204, 1, 0);">]</span>)</div>
<p style="margin: 0px; font: 13px Menlo; color: rgb(51, 50, 153);"> </p><div style="margin: 0px; line-height: 18px; color: rgb(51, 50, 153);">run n <span style="color: rgb(204, 1, 0);">=</span> <span style="text-decoration: underline; color: rgb(58, 50, 255);">foldl</span> (flip pass) (replicate n <span style="color: rgb(19, 153, 17);"><b>Closed</b></span>) <span style="color: rgb(204, 1, 0);">[</span><span style="color: rgb(255, 51, 51);">0</span>..n<span style="color: rgb(204, 1, 0);">]</span></div>
</div><div><br></div><div>Do I need to add run 100 to the end of the example for it to actually do something?</div></div><br>_______________________________________________<br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Rafael Gustavo da Cunha Pereira Pinto<br><br>