Minor tweak to project-euler

extra/project-euler/150/150.factor

@@ -1,15 +1,21 @@
 ! Copyright (c) 2008 Eric Mertens
 ! See http://factorcode.org/license.txt for BSD license.
-USING: kernel math sequences locals ;
+USING: kernel math sequences sequences.private locals hints ;
 IN: project-euler.150
 
 <PRIVATE
 
 ! sequence helper functions
 
-: partial-sums ( seq -- seq )
+: partial-sums ( seq -- sums )
     0 [ + ] accumulate swap suffix ; inline
 
+: (partial-sum-infimum) ( inf sum elt -- inf sum )
+    + [ min ] keep ; inline
+
+: partial-sum-infimum ( seq -- seq )
+    0 0 rot [ (partial-sum-infimum) ] each drop ; inline
+
 : generate ( n quot -- seq )
     [ drop ] swap compose map ; inline
 
@@ -20,25 +26,27 @@ IN: project-euler.150
 ! triangle generator functions
 
 : next ( t -- new-t s )
-    615949 * 797807 + 1 20 shift mod dup 1 19 shift - ; inline
+    615949 * 797807 + 20 2^ rem dup 19 2^ - ; inline
 
 : sums-triangle ( -- seq )
-    0 1000 [ 1+ [ next ] generate partial-sums ] map nip ;
+    0 1000 [ 1+ [ next ] generate partial-sums ] map nip ; 
 
-PRIVATE>
+PRIVATE> USING: arrays kernel.private ;
 
 :: (euler150) ( m -- n )
     [let | table [ sums-triangle ] |
         m [| x |
             x 1+ [| y |
                 m x - [| z |
-                    x z + table nth
-                    [ y z + 1+ swap nth ]
-                    [ y        swap nth ] bi -
-                ] map partial-sums infimum
+                    x z + table nth-unsafe
+                    [ y z + 1+ swap nth-unsafe ]
+                    [ y        swap nth-unsafe ] bi -
+                ] map partial-sum-infimum
             ] map-infimum
         ] map-infimum
     ] ;
 
+HINTS: (euler150) fixnum ;
+
 : euler150 ( -- n )
     1000 (euler150) ;