On 22/12/2009 1:16 p.m., Nick Sabalausky wrote:
"Tim Matthews"<[email protected]> wrote in message
news:[email protected]...
On 21/12/2009 8:57 p.m., Don wrote:
retard wrote:
Sun, 20 Dec 2009 16:44:03 +0100, Don wrote:
downs wrote:
according to
http://www.mail-archive.com/haskell-cafe%40haskell.org/msg63381.html
I'll let this speak for itself.
import Data.Array.Base (unsafeRead, unsafeWrite)
[snip]
Brilliant.
What is so brilliant? Referential transparency is broken unless single-
threadedness is forced through monadic computation or by some other
means (uniqueness types comes to mind).
The brilliant bit is the idea of doing a fairer comparison of quicksort
between D and Haskell.
Quicksort can be expressed in haskell just like this:
qsort [] = []
qsort (x:xs) = qsort (filter (< x) xs) ++ [x] ++ qsort (filter (>= x) xs)
It probably performs like a bitch but is a very beautiful way to express
quicksort.
Quicksort is in-place and doesn't use the head as the pivot.
true
Besides "It probably performs like a bitch" defeats the whole point of
quicksort, doesn't it?
true
And, going along with what Andrei pointed out in
another thread, it's hard call a piece of code "beautiful" if it's either
flat-out wrong or otherwise defeats its own point.
My stance on this is that the qsort code explains how you want the code
to be sorted and a really good haskell compiler should optimize that
out. Infact as haskell can't update in place anything without
interfacing to c, I often blame the compiler but realistically most
still have some way to go for that kind of optimizations.
As for the qsort algorithm using the head as the pivot. Thanks for
pointing that out. I didn't write it but I copy/pasted it from the
official wiki
http://www.haskell.org/haskellwiki/Introduction#Quicksort_in_Haskell
Another place that describe quicksort in haskell and also a wiki incase
you want to edit it http://en.literateprograms.org/Quicksort_%28Haskell%29
