Hello Haskell-ers,<br>So a friend and I were thinking about making code faster in Haskell, and I was wondering if there was a way to improve the following method of generating the list of all prime numbers.&nbsp; It takes about 13 seconds to run, meanwhile my friend&#39;s C version took 
0.1.&nbsp; I&#39;d love to learn a bit more about how to optimize Haskell code.<br><br>Cheers, <br>Creighton Hogg<br><br>-- Naive way to calculate prime numbers, testing each new n to see if it has prime factors less than sqrt(n).
<br>import Data.List<br>primes = 2:(foldr (\x y -&gt; if isPrime x then x:y else y) [] [3..])<br>&nbsp;&nbsp;&nbsp; where isPrime x = foldl&#39; (\z y -&gt; z &amp;&amp; (if x `mod` y == 0 then False else True)) True (take (floor $ sqrt $ fromIntegral x) primes)
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