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 <bo@ct.de> (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) Affe Apfel Vergaser /* Heise Zeitschriften Verlag GmbH & Co. KG * Karl-Wiechert-Allee 10 * 30625 Hannover * Registergericht: Amtsgericht Hannover HRA 26709 * Persönlich haftende Gesellschafterin: Heise Zeitschriften Verlag * Geschäftsführung GmbH * Registergericht: Amtsgericht Hannover, HRB 60405 * Geschäftsführer: Ansgar Heise, Dr. Alfons Schräder */