mihai@keldon:/tmp$ cat 1.hs
fact n = product [1..n]
main = print $ fact 10000
mihai@keldon:/tmp$ ghc --make -O 1.hs &> /dev/null
mihai@keldon:/tmp$ time ./1 > /dev/null

real	0m0.058s
user	0m0.052s
sys	0m0.004s
mihai@keldon:/tmp$ vi 1.hs
mihai@keldon:/tmp$ cat 1.hs
fact n = product [1..n]
main = print $ fact 100000
mihai@keldon:/tmp$ ghc --make -O 1.hs &> /dev/null
mihai@keldon:/tmp$ time ./1 > /dev/null

real	0m4.303s
user	0m4.212s
sys	0m0.076s