Revert "math.statistics: change cum-mean to use v/."

This reverts commit 9df2235d8983da67d106a6d5fb297134e5e2a58e.

basis/math/combinatorics/combinatorics.factor

@@ -17,72 +17,6 @@ IN: math.combinatorics
 
 PRIVATE>
 
-<PRIVATE
-
-: (binary-reduce2) ( ... seq start quot: ( ... elt1 elt2 -- ... newelt ) from length -- ... value )
-    #! We can't use case here since combinators depends on
-    #! sequences
-    dup 4 < [
-        integer>fixnum {
-            [ 2drop nip ]
-            [ 2nip swap nth-unsafe ]
-            [ -rot [ drop swap nth2-unsafe ] dip call ]
-            [ -rot [ drop swap nth3-unsafe ] dip bi@ ]
-        } dispatch
-    ] [
-        [ 2/ ] [ over - ] bi [ 2dup + ] dip
-        [ (binary-reduce) ] [ 2curry ] curry 2bi@
-        pick [
-            [ 3curry ] bi-curry@ 3bi
-            [ call ] dip swap [ call ] dip
-        ] dip call
-    ] if ; inline recursive
-
-PRIVATE>
-
-: binary-reduce2 ( ... seq start quot: ( ... elt1 elt2 -- ... newelt ) -- ... value )
-    pick length 0 max 0 swap (binary-reduce2) ; inline
-
-GENERIC: sum2 ( seq -- n )
-M: object sum2 0 [ + ] binary-reduce2 ;
-
-GENERIC: sum3 ( seq -- n )
-M: object sum3 0 [ + ] binary-reduce ;
-
-: product2 ( seq -- n )
-    0 swap 1 [
-        dup even? [ 2/ * [ 1 + ] dip ] [ * ] if
-    ] binary-reduce2 swap shift ;
-
-TUPLE: factorials n length ;
-: <factorials> ( n -- factorials )
-    dup dup odd? [ 1 + ] when 2/ factorials boa ; inline
-M: factorials length length>> ; inline
-M: factorials nth-unsafe
-    n>> swap [ - ] keep 1 + 2dup = [ drop ] [ * ] if ; inline
-INSTANCE: factorials sequence
-
-: factorial-product ( n -- n! )
-    dup 1 > [ [1,b] product2 ] [ drop 1 ] if ;
-
-: factorial1 ( n -- n! )
-    dup 1 > [
-        [ 0 1 ] dip [ dup 1 > ] [
-            [ dup even? [ 2/ [ 1 + ] 2dip ] when * ]
-            [ 1 - ] bi
-        ] while drop swap shift
-    ] [ drop 1 ] if ;
-
-: factorial0 ( n -- n! )
-    dup 1 > [ [1,b] product ] [ drop 1 ] if ;
-
-:: factorial2 ( n -- n! )
-    n n n [ 2 - dup 1 > ] [
-        [ + [ * ] keep ] keep
-    ] while nip 1 = [ n 1 + 2/ * ] when ;
-
-! http://www.luschny.de/math/factorial/scala/FactorialScalaCsharp.htm
-
 MEMO: factorial ( n -- n! )
     dup 1 > [ [1,b] product ] [ drop 1 ] if ;
 

basis/math/statistics/statistics.factor

@@ -350,9 +350,9 @@ ALIAS: std sample-std
 
 : cum-product ( seq -- seq' )
     1 [ * ] cum-map ;
-
+    
 : cum-mean ( seq -- seq' )
-    [ cum-sum ] [ length [1,b] ] bi v/ ;
+    [ cum-sum ] [ length [1,b] ] bi [ / ] 2map ;    
 
 : cum-count ( seq quot -- seq' )
     [ 0 ] dip '[ _ call [ 1 + ] when ] cum-map ; inline