RosettaCodeData/Task/Move-to-front-algorithm/Factor/move-to-front-algorithm.factor

19 lines
575 B
Factor

USING: formatting kernel locals make sequences ;
: to-front ( elt seq -- seq' ) over [ remove ] dip prefix ;
: encode ( symbols msg -- indices )
[ [ swap 2dup index , to-front ] each ] { } make nip ;
: decode ( symbols indices -- msg )
[ [ swap [ nth ] keep over , to-front ] each ] "" make nip ;
:: round-trip ( msg symbols -- )
symbols msg encode :> encoded
symbols encoded decode :> decoded
msg decoded assert=
msg encoded decoded "%s -> %u -> %s\n" printf ;
"broood" "bananaaa" "hiphophiphop"
[ "abcdefghijklmnopqrstuvwxyz" round-trip ] tri@