factor: trim using lists

[factor.git] / extra / project-euler / 150 / 150.factor

diff --git a/extra/project-euler/150/150.factor b/extra/project-euler/150/150.factor
index eeb4b0c315eb82420b8db813dd3c1d1ddacf650b..8891fe62160a74848b7533c09a778109c0c3f6c9 100644 (file)
--- a/extra/project-euler/150/150.factor
+++ b/extra/project-euler/150/150.factor
@@ -1,7 +1,7 @@
 ! Copyright (c) 2008 Eric Mertens.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: hints kernel locals math math.order math.ranges project-euler.common
-    sequences sequences.private ;
+USING: kernel math math.order ranges math.statistics
+project-euler.common sequences sequences.private ;
 IN: project-euler.150
 
 ! http://projecteuler.net/index.php?section=problems&id=150
@@ -34,13 +34,10 @@ IN: project-euler.150
 ! sequence helper functions
 
 : partial-sums ( seq -- sums )
-    0 [ + ] accumulate swap suffix ; inline
+    cum-sum 0 prefix ; 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
+: partial-sum-infimum ( seq quot -- seq )
+    [ 0 0 ] 2dip [ + [ min ] keep ] compose each drop ; inline
 
 : map-infimum ( seq quot -- min )
     [ min ] compose 0 swap reduce ; inline
@@ -51,22 +48,19 @@ IN: project-euler.150
     615949 * 797807 + 20 2^ rem dup 19 2^ - ; inline
 
 : sums-triangle ( -- seq )
-    0 1000 [1,b] [ [ next ] replicate partial-sums ] map nip ;
+    0 1000 [1..b] [ [ next ] replicate partial-sums ] map nip ; inline
 
 :: (euler150) ( m -- n )
-    [let | table [ sums-triangle ] |
-        m [| x |
-            x 1+ [| y |
-                m x - [0,b) [| z |
-                    x z + table nth-unsafe
-                    [ y z + 1+ swap nth-unsafe ]
-                    [ y        swap nth-unsafe ] bi -
-                ] map partial-sum-infimum
-            ] map-infimum
+    sums-triangle :> table
+    m <iota> [| x |
+        x 1 + <iota> [| y |
+            m x - <iota> [| z |
+                x z + table nth-unsafe
+                [ y z + 1 + swap nth-unsafe ]
+                [ y         swap nth-unsafe ] bi -
+            ] partial-sum-infimum
         ] map-infimum
-    ] ;
-
-HINTS: (euler150) fixnum ;
+    ] map-infimum ; inline
 
 PRIVATE>