Change how sequence>assoc and friends work. Now they take two quotations, the first of which prepares the key/value pair and the second insert it into the assoc. mrjbq7's group-by, formerly collect-values, is now called collect-by.

basis/math/statistics/statistics-docs.factor

@@ -112,41 +112,42 @@ HELP: sorted-histogram
 
 HELP: sequence>assoc
 { $values
-    { "seq" sequence } { "quot" quotation } { "exemplar" "an exemplar assoc" }
+    { "seq" sequence } { "quot1" quotation } { "quot2" quotation } { "exemplar" "an exemplar assoc" }
     { "assoc" assoc }
 }
-{ $description "Iterates over a sequence, allowing elements of the sequence to be added to a newly created " { $snippet "assoc" } " according to the passed quotation." }
+{ $description "Iterates over a sequence, allowing elements of the sequence to be added to a newly created " { $snippet "assoc" } ". The first quotation gets passed an element from the sequence and should output whatever the second quotation needs, e.g. ( element -- value key ) if the second quotation is inserting into an assoc." }
 { $examples
     { $example "! Iterate over a sequence and increment the count at each element"
+               "! The first quotation has stack effect ( key -- key ), a no-op"
                "USING: assocs prettyprint math.statistics ;"
-               "\"aaabc\" [ inc-at ] H{ } sequence>assoc ."
+               "\"aaabc\" [ ] [ inc-at ] H{ } sequence>assoc ."
                "H{ { 97 3 } { 98 1 } { 99 1 } }"
     }
 } ;
 
 HELP: sequence>assoc!
 { $values
-    { "assoc" assoc } { "seq" sequence } { "quot" quotation }
+    { "assoc" assoc } { "seq" sequence } { "quot1" quotation } { "quot2" quotation }
 }
-{ $description "Iterates over a sequence, allowing elements of the sequence to be added to an existing " { $snippet "assoc" } " according to the passed quotation." }
+{ $description "Iterates over a sequence, allowing elements of the sequence to be added to an existing " { $snippet "assoc" } ". The first quotation gets passed an element from the sequence and should output whatever the second quotation needs, e.g. ( element -- value key ) if the second quotation is inserting into an assoc." }
 { $examples
     { $example "! Iterate over a sequence and add the counts to an existing assoc"
                "USING: assocs prettyprint math.statistics kernel ;"
-               "H{ { 97 2 } { 98 1 } } clone \"aaabc\" [ inc-at ] sequence>assoc! ."
+               "H{ { 97 2 } { 98 1 } } clone \"aaabc\" [ ] [ inc-at ] sequence>assoc! ."
                "H{ { 97 5 } { 98 2 } { 99 1 } }"
     }
 } ;
 
 HELP: sequence>hashtable
 { $values
-    { "seq" sequence } { "quot" quotation }
+    { "seq" sequence } { "quot1" quotation } { "quot2" quotation }
     { "hashtable" hashtable }
 }
-{ $description "Iterates over a sequence, allowing elements of the sequence to be added to a hashtable according to the passed quotation." }
+{ $description "Iterates over a sequence, allowing elements of the sequence to be added to a hashtable according a combination of the first and second quotations. The quot1 is passed each element, and quot2 gets the hashtable on the top of the stack with quot1's results underneath for inserting into the hashtable." }
 { $examples
     { $example "! Count the number of times an element occurs in a sequence"
                "USING: assocs prettyprint math.statistics ;"
-               "\"aaabc\" [ inc-at ] sequence>hashtable ."
+               "\"aaabc\" [ ] [ inc-at ] sequence>hashtable ."
                "H{ { 97 3 } { 98 1 } { 99 1 } }"
     }
 } ;

basis/math/statistics/statistics.factor

@@ -1,8 +1,7 @@
 ! Copyright (C) 2008 Doug Coleman, Michael Judge.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: arrays combinators kernel math math.functions
+USING: assocs combinators generalizations kernel locals math
-math.order sequences sorting locals sequences.private
+math.functions math.order sequences sequences.private sorting ;
-assocs fry ;
 IN: math.statistics
 
 : mean ( seq -- x )
@@ -59,31 +58,34 @@ IN: math.statistics
 
 <PRIVATE
 
-: (sequence>assoc) ( seq quot assoc -- assoc )
+: (sequence>assoc) ( seq quot1 quot2 assoc -- assoc )
-    [ swap curry each ] keep ; inline
+    [ swap curry compose each ] keep ; inline
 
 PRIVATE>
 
-: sequence>assoc! ( assoc seq quot: ( obj assoc -- ) -- assoc )
+: sequence>assoc! ( assoc seq quot1 quot2 -- assoc )
-    rot (sequence>assoc) ; inline
+    4 nrot (sequence>assoc) ; inline
 
-: sequence>assoc ( seq quot: ( obj assoc -- ) exemplar -- assoc )
+: sequence>assoc ( seq quot1 quot2 exemplar -- assoc )
     clone (sequence>assoc) ; inline
 
-: sequence>hashtable ( seq quot: ( obj hashtable -- ) -- hashtable )
+: sequence>hashtable ( seq quot1 quot2 -- hashtable )
     H{ } sequence>assoc ; inline
 
 : histogram! ( hashtable seq -- hashtable )
-    [ inc-at ] sequence>assoc! ;
+    [ ] [ inc-at ] sequence>assoc! ;
 
 : histogram ( seq -- hashtable )
-    [ inc-at ] sequence>hashtable ;
+    [ ] [ inc-at ] sequence>hashtable ;
 
 : sorted-histogram ( seq -- alist )
     histogram >alist sort-values ;
 
-: collect-values ( seq quot: ( obj hashtable -- ) -- hash )
+: collect-pairs ( seq quot -- hashtable )
-    '[ [ dup @ ] dip push-at ] sequence>hashtable ; inline
+    [ push-at ] sequence>hashtable ; inline
+
+: collect-by ( seq quot -- hashtable )
+    [ dup ] prepose collect-pairs ; inline
 
 : mode ( seq -- x )
     histogram >alist