21 lines
661 B
Factor
21 lines
661 B
Factor
|
|
USING: kernel namespaces arrays quotations sequences assocs combinators
|
|
mirrors math math.vectors random combinators.lib macros bake ;
|
|
|
|
IN: random-weighted
|
|
|
|
: probabilities ( weights -- probabilities ) dup sum [ / ] curry map ;
|
|
|
|
: layers ( probabilities -- layers )
|
|
dup length 1+ [ head ] curry* map 1 tail [ sum ] map ;
|
|
|
|
: random-weighted ( weights -- elt )
|
|
probabilities layers [ 1000 * ] map 1000 random [ > ] curry find drop ;
|
|
|
|
: random-weighted* ( seq -- elt )
|
|
dup [ second ] map swap [ first ] map random-weighted swap nth ;
|
|
|
|
MACRO: call-random-weighted ( exp -- )
|
|
[ keys ] [ values <enum> >alist ] bi swap
|
|
[ , random-weighted , case ] bake ;
|