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POWhy directly imported functions in GHC differ so much with functions I write with the source code copied from GHC Libraries
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copied!<pre><code>module Has (r,p,s) where import Prelude ((==),Bool(..),otherwise,(||),Eq) import qualified Data.List as L filter :: (a -> Bool) -> [a] -> [a] filter _pred [] = [] filter pred (x:xs) | pred x = x : filter pred xs | otherwise = filter pred xs </code></pre> <p>problem1: This <code>filter</code> is copied from <code>GHC</code>'s library, but why it consumes a growing number of memory <em>in contrast with</em> the directly imported <code>filter</code>, which consumes a constant number of memory.</p> <pre><code>elem :: (Eq a) => a -> [a] -> Bool elem _ [] = False elem x (y:ys) = x==y || elem x ys </code></pre> <p>problem2: This <code>filter</code> is copied from <code>GHC</code>'s library, but why it consumes a growing number of memory <em>like</em> the directly used <code>elem</code>, which <em>also</em> consumes a growing number of memory <em>in contrast with</em> the directly imported <code>filter</code>.</p> <pre><code>r = L.filter (==1000000000000) [0..] p = filter (==1000000000000) [0..] s = 1000000000000 `elem` [0..] </code></pre> <p>GHC version:7.4.2 OS:Ubuntu 12.10 Compiled with -O2 to optimize</p> <p>As the above <code>filter</code> and <code>elem</code> 's definitions imply both <code>p = filter (==1000000000000) [0..]</code> and <code>s = 1000000000000 `elem` [0..]</code> 's <code>[0..]</code> should be garbage collected gradually. But both <code>p</code> and <code>s</code> consumes a growing number of memory. And <code>r</code> which is defined with the directly imported <code>filter</code> consumes a constant number of memory.</p> <p>My question is why directly imported functions in GHC differ so much with functions I write with the source code copied from GHC Libraries. I wonded if there is something wrong with GHC?</p> <p>I has a further question: The above code is abstracted from a project I writed, and the project also faces the problem of "consumes a growing number of memory, which should be garbage collected in theory". So I want to know that is there a way to find which variable takes up so much memory in GHC.</p> <p>Thanks for your reading.</p>

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