September Morn Update

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

@@ -0,0 +1,18 @@
+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@