From 38a5184fdf123d7a9afe7801f7f4d065868da5f3 Mon Sep 17 00:00:00 2001
From: Joe Groff <arcata@gmail.com>
Date: Mon, 31 Oct 2011 18:55:21 -0700
Subject: [PATCH] math.statistics: fix stack effect on collect-by

---
 basis/math/statistics/statistics-tests.factor | 11 ++++++++++-
 basis/math/statistics/statistics.factor       |  4 ++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/basis/math/statistics/statistics-tests.factor b/basis/math/statistics/statistics-tests.factor
index 0d3172f685..ec6cda05b1 100644
--- a/basis/math/statistics/statistics-tests.factor
+++ b/basis/math/statistics/statistics-tests.factor
@@ -1,4 +1,4 @@
-USING: kernel math math.functions math.statistics tools.test ;
+USING: assocs kernel math math.functions math.statistics sequences tools.test ;
 IN: math.statistics.tests
 
 [ 1 ] [ { 1 } mean ] unit-test
@@ -53,3 +53,12 @@ IN: math.statistics.tests
 ] [
     "aabbcc" histogram
 ] unit-test
+
+{
+    V{ 0 3 6 9 }
+    V{ 1 4 7 }
+    V{ 2 5 8 }
+} [
+    10 iota [ 3 mod ] collect-by
+    [ 0 swap at ] [ 1 swap at ] [ 2 swap at ] tri
+] unit-test
diff --git a/basis/math/statistics/statistics.factor b/basis/math/statistics/statistics.factor
index 46b24bc98b..54edff34a4 100644
--- a/basis/math/statistics/statistics.factor
+++ b/basis/math/statistics/statistics.factor
@@ -84,10 +84,10 @@ PRIVATE>
 : sorted-histogram ( seq -- alist )
     histogram sort-values ;
 
-: collect-pairs ( seq quot: ( x -- x' ) -- hashtable )
+: collect-pairs ( seq quot: ( x -- v k ) -- hashtable )
     [ push-at ] sequence>hashtable ; inline
 
-: collect-by ( seq quot -- hashtable )
+: collect-by ( seq quot: ( x -- x' ) -- hashtable )
     [ dup ] prepose collect-pairs ; inline
 
 : mode ( seq -- x )