z-algorithm: slightly faster by allocating and using an array.

extra/z-algorithm/z-algorithm.factor

@@ -1,38 +1,39 @@
 ! Copyright (C) 2010 Dmitry Shubin.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: arrays combinators.smart kernel locals math math.ranges
-sequences sequences.private ;
+USING: arrays kernel locals math math.ranges sequences
+sequences.private ;
 IN: z-algorithm
 
 : lcp ( seq1 seq2 -- n )
-    [ min-length ] 2keep mismatch [ nip ] when* ;
+    [ min-length dup ] 2keep mismatch-unsafe [ nip ] when* ;
 
 <PRIVATE
 
 :: out-of-zbox ( seq Z l r k -- seq Z l r )
     seq k tail-slice seq lcp :> Zk
-    Zk Z push seq Z
+    Zk k Z set-nth seq Z
     Zk 0 > [ k Zk k + 1 - ] [ l r ] if ; inline
 
 :: inside-zbox ( seq Z l r k -- seq Z l r )
     k l - Z nth :> Zk'
     r k - 1 +   :> b
     seq Z Zk' b <
-    [ Zk' Z push l r ] ! still inside
+    [ Zk' k Z set-nth l r ] ! still inside
     [
         seq r 1 + seq b [ tail-slice ] 2bi@ lcp :> q
-        q b + Z push k q r +
+        q b + k Z set-nth k q r +
     ] if ; inline
 
-: (z-value) ( seq Z l r k -- seq Z l r )
+: z-value ( seq Z l r k -- seq Z l r )
     2dup < [ out-of-zbox ] [ inside-zbox ] if ; inline
 
 :: (z-values) ( seq -- Z )
-    V{ } clone 0 0 seq length :> ( Z l r len )
-    len Z push [ seq Z l r 1 len [a,b) [ (z-value) ] each ]
-    drop-outputs Z ; inline
+    seq length dup 0 <array> :> ( len Z )
+    len 0 Z set-nth
+    seq Z 0 0 len [1,b) [ z-value ] each 4drop
+    Z ; inline
 
 PRIVATE>
 
 : z-values ( seq -- Z )
-    dup length 0 > [ (z-values) ] when >array ;
+    [ { } ] [ (z-values) ] if-empty ;