From 827faa205c661af763dd916385330475a2dac8b0 Mon Sep 17 00:00:00 2001
From: Aaron Schaefer <aaron@elasticdog.com>
Date: Fri, 18 Jan 2008 20:07:41 -0500
Subject: [PATCH] Alternate solution to Project Euler problem 2

---
 extra/project-euler/002/002.factor | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/extra/project-euler/002/002.factor b/extra/project-euler/002/002.factor
index 55c1b153cc..b0b21e76e1 100644
--- a/extra/project-euler/002/002.factor
+++ b/extra/project-euler/002/002.factor
@@ -1,6 +1,6 @@
 ! Copyright (c) 2007 Aaron Schaefer.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: kernel math sequences ;
+USING: kernel math sequences shuffle ;
 IN: project-euler.002
 
 ! http://projecteuler.net/index.php?section=problems&id=2
@@ -35,4 +35,18 @@ PRIVATE>
 ! [ euler002 ] 100 ave-time
 ! 0 ms run / 0 ms GC ave time - 100 trials
 
-MAIN: euler002
+
+! ALTERNATE SOLUTIONS
+! -------------------
+
+: fib-upto* ( n -- seq )
+    0 1 [ pick over >= ] [ tuck + dup ] [ ] unfold 3nip
+    1 head-slice* { 0 1 } swap append ;
+
+: euler002a ( -- answer )
+    1000000 fib-upto* [ even? ] subset sum ;
+
+! [ euler002a ] 100 ave-time
+! 0 ms run / 0 ms GC ave time - 100 trials
+
+MAIN: euler002a