Hi everybody,<br><br>after reading a post by Don Stewart on <a href="http://cgi.cse.unsw.edu.au/~dons/blog/2008/05/16#fast">http://cgi.cse.unsw.edu.au/~dons/blog/2008/05/16#fast</a>, I was not really satisfied with the necessity to rewrite<br>
<br><span style="font-family: courier new,monospace;">mean xs = sum xs / fromIntegral (length xs)</span><br><br>to an explicitly recursive function. I investigated a bit further and got really confused after the following GHCi session:<br>
<br><span style="font-family: courier new,monospace;">Prelude&gt; length [1..10^8] + length [1..10^8]</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">200000000</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">Prelude&gt; let xs = [1..10^8]</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">Prelude&gt; length xs + length xs</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">&lt;interactive&gt;: out of memory</span><br><br>Can someone explain this and give a simple, reasonable rule by which I can predict such things in the future? Isn&#39;t it a pitfall?<br>
<br>Tim<br><br>