From: Doug Coleman <doug.coleman@gmail.com>
Date: Sat, 26 Mar 2022 00:50:10 +0000 (-0500)
Subject: assocs.extras: Add a histogram-diff for fun.
X-Git-Tag: 0.99~1470
X-Git-Url: https://gitweb.factorcode.org/gitweb.cgi?p=factor.git;a=commitdiff_plain;h=cd194eebbf3bfc8ab795b41f99613faae342df34

assocs.extras: Add a histogram-diff for fun.
---

diff --git a/extra/assocs/extras/extras.factor b/extra/assocs/extras/extras.factor
index 9a6ba7553e..69a2c3cbce 100644
--- a/extra/assocs/extras/extras.factor
+++ b/extra/assocs/extras/extras.factor
@@ -230,3 +230,7 @@ PRIVATE>
 : collect-value-by ( ... seq quot: ( ... obj -- ... key ) -- ... assoc )
     [ keep swap ] curry H{ } clone
     [ '[ @ [ second ] dip _ push-at ] each ] keep ; inline
+
+: histogram-diff ( hashtable1 hashtable2 -- hashtable3 )
+    [ neg swap pick at+ ] assoc-each
+    [ 0 > ] filter-values ;