[Haskell-cafe] Shouldnt this be lazy too?
j.vimal at gmail.com
Mon Sep 24 13:01:35 EDT 2007
>From the wiki:
> If you write it, you force Haskell to create all list nodes. ...
Now, lets look at the definition again:
> length  = 0
> length (x:xs) = 1 + length xs
We see that the value of *x* isnt needed at all. So, why does GHC
allocate so much memory creating all those *x*s? because, if we have:
length [1..] = 1 + length [2...] = 1 + 1 + length [3...]
This should go on, into an infinite loop. GHC doesnt need to create
all nodes! The wiki also claims that *x* isnt evaluated. So, why
allocate space for it when its not evaluated?
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