[Haskell-beginners] Factorials using foldx
Paul Johnston
paul.a.johnston at manchester.ac.uk
Thu Aug 7 10:16:04 EDT 2008
Hi (First question so be gentle)!
Just started to look at Haskell and I was wondering about various versions of calculating factorials.
If I have
facr 0 = 1
facr n = foldr (*) 1 [1..n]
facl 0 = 1
facl n = foldl (*) 1 [1..n]
Is there any difference in efficiency, I remember reading it is better to count down than to count up but left to right or right to left :-)
Cheers Paul
Paul Johnston
Humanities Development Team
Room 2.12
Bridgeford Street Building
Manchester University
Tel 0161 275 1396
Mail Paul.Johnston at manchester.ac.uk
Web http://web-1.humanities.manchester.ac.uk/prjs/mcasspj/
How to shoot yourself in the foot
Unix
% ls
foot.c foot.h foot.o toe.d toe.o
%rm* .o
rm:.o no such file or directory
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