Merge branch 'master' of http://factorforge.org/glguy.factor

extra/project-euler/148/148.factor

@@ -0,0 +1,24 @@
+! Copyright (c) 2008 Eric Mertens
+! See http://factorcode.org/license.txt for BSD license.
+USING: kernel math math.functions sequences sequences.lib ;
+
+IN: project-euler.148
+
+<PRIVATE
+
+: sum-1toN ( n -- sum )
+    dup 1+ * 2/ ; inline
+
+: >base7 ( x -- y )
+    [ dup 0 > ] [ 7 /mod ] [ ] unfold nip ;
+
+: (use-digit) ( prev x index -- next )
+    [ [ 1+ * ] [ sum-1toN 7 sum-1toN ] bi ] dip ^ * + ;
+
+PRIVATE>
+
+: (euler148) ( x -- y )
+    >base7 0 [ (use-digit) ] reduce-index ;
+
+: euler148 ( -- y )
+    10 9 ^ (euler148) ;

extra/sequences/lib/lib.factor

@@ -35,6 +35,10 @@ MACRO: firstn ( n -- )
     #! quot: ( elt index -- obj )
     prepare-index 2map ; inline
 
+: reduce-index ( seq identity quot -- )
+    #! quot: ( prev elt index -- next )
+    swapd each-index ; inline
+
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
 : each-percent ( seq quot -- )