[Haskell-cafe] Sub-optimal [code]

Andrew Coppin andrewcoppin at btinternet.com
Tue Feb 15 23:29:39 CET 2011

On 15/02/2011 08:35 PM, Daniel Fischer wrote:

> The result is that the list
> [1 .. 10*1024*1024*k]
> from the penultimate line of random_file is shared between the four
> iterations of the inner loop in file_batch (for k = 1 .. 4). Oops.

Ouch! That's gotta sting in the morning... o_O

I suppose what we could really do with is a combinator that runs a 
monadic action N times, without actually constructing a list N elements 
long in order to do so. Then it becomes blatently obvious that there's 
nothing to share, and the problem goes away.

They say that in Haskell, "a list *is* a loop". Apparently, not always. ;-)

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