 IN: combinators.random
 
 : ifp ( p true false -- ) [ random-unit > ] 2dip if ; inline
+
 : whenp ( p true -- ) [ ] ifp ; inline
+
 : unlessp ( p false -- ) [ [ ] ] dip ifp ; inline
 
 <PRIVATE


M: bad-probabilities summary
    drop "The probabilities do not satisfy the rules stated in the docs." ;
    
: good-probabilities? ( assoc -- ? )
    dup last pair? [
        keys { [ sum 1 number= ] [ [ 0 1 between? ] all? ] } 1&&

        [ dup pair? [ prepare-pair ] [ with-drop ] if ] map
        cond>quot
    ] [ bad-probabilities ] if ;

MACRO: (casep) ( assoc -- ) (casep>quot) ;

: casep>quot ( assoc -- quot )
    (casep>quot) [ random-unit ] prepend ;

: (conditional-probabilities) ( seq i -- p )
    [ dup 0 > [ head [ 1 swap - ] [ * ] map-reduce ] [ 2drop 1 ] if ]
    [ swap nth ] 2bi * ;

: conditional-probabilities ( seq -- seq' )
    dup length iota [ (conditional-probabilities) ] with map ;

: (direct>conditional) ( assoc -- assoc' )
    [ keys conditional-probabilities ] [ values ] bi zip ;

: direct>conditional ( assoc -- assoc' )
    dup last pair? [ (direct>conditional) ] [
        unclip-last [ (direct>conditional) ] [ suffix ] bi*
