Am 26.09.12 10:09, schrieb Daniel Trstenjak:
Hi Harald,
how do I (quickly) pick a random element from a `Data.Map.Map`?
[..]
M.keys map !! randomValue `mod` M.size map
But if you need a high performance solution than it's more appropriate
to put the values into a Data.Vector and indexing into it.
I was hoping to find a solution that makes use of the specific structure
of a map, but now I have written it like this and it works for me:
let (r, gen') = randomR (0, Map.size m - 1) gen
in (Map.keys m !! r, gen')
Thanks for the hint!
Harald
--
Harald Bögeholz (PGP key available from servers)
Redaktion c't Tel.: +49 511 5352-300 Fax: +49 511 5352-417
http://www.ct.de/
int f[9814],b,c=9814,g,i;long a=1e4,d,e,h;
main(){for(;b=c,c-=14;i=printf("%04d",e+d/a),e=d%a)
while(g=--b*2)d=h*b+a*(i?f[b]:a/5),h=d/--g,f[b]=d%g;}
(Arndt/Haenel)
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