From baa7f3b31f3686dd30a70a3a32566c3097068e5d Mon Sep 17 00:00:00 2001
From: Doug Coleman <doug.coleman@gmail.com>
Date: Sat, 20 Aug 2022 17:50:04 -0400
Subject: [PATCH] assocs.extras: add intersect-keys-as and unit tests

---
 extra/assocs/extras/extras-tests.factor | 9 +++++++++
 extra/assocs/extras/extras.factor       | 5 ++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/extra/assocs/extras/extras-tests.factor b/extra/assocs/extras/extras-tests.factor
index c8233c6d25..cf7ce6ce37 100644
--- a/extra/assocs/extras/extras-tests.factor
+++ b/extra/assocs/extras/extras-tests.factor
@@ -296,3 +296,12 @@ USING: arrays assocs.extras kernel math math.order sequences tools.test ;
     [ [ dup 1 + 2array ] dip ] collect-assoc-by-multi
 ] unit-test
 
+{ H{ { 1 2 } { 3 4 } } } [
+    H{ { 1 2 } { 3 4 } { 5 6 } }
+    { 1 3 } intersect-keys
+] unit-test
+
+{ { { 1 2 } { 3 4 } } } [
+    H{ { 1 2 } { 3 4 } { 5 6 } }
+    { 1 3 } { } intersect-keys-as
+] unit-test
diff --git a/extra/assocs/extras/extras.factor b/extra/assocs/extras/extras.factor
index 8aee7d6d9d..7073a07438 100644
--- a/extra/assocs/extras/extras.factor
+++ b/extra/assocs/extras/extras.factor
@@ -217,8 +217,11 @@ PRIVATE>
 : flatten-values ( assoc -- assoc' )
     dup any-multi-value? [ expand-values-set-at flatten-values ] when ;
 
+: intersect-keys-as ( assoc seq exemplar -- elts )
+  [ [ of ] with ] dip zip-with-as sift-values ; inline
+
 : intersect-keys ( assoc seq -- elts )
-    [ of ] with zip-with sift-values ; inline
+    over intersect-keys-as ; inline
 
 : values-of ( assoc seq -- seq' )
     [ of ] with map ; inline
-- 
2.34.1