From cd94b89a9bc52d14abbf852e59bad4137e97267f Mon Sep 17 00:00:00 2001
From: John Benediktsson <mrjbq7@gmail.com>
Date: Sat, 6 Aug 2022 09:07:08 -0700
Subject: [PATCH] sequences.extras: adding map-if

---
 extra/sequences/extras/extras-tests.factor | 2 ++
 extra/sequences/extras/extras.factor       | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/extra/sequences/extras/extras-tests.factor b/extra/sequences/extras/extras-tests.factor
index 38455fb448..23100570db 100644
--- a/extra/sequences/extras/extras-tests.factor
+++ b/extra/sequences/extras/extras-tests.factor
@@ -294,3 +294,5 @@ tools.test vectors vocabs ;
 { { } } [
     { } [ nip ] map-with-previous
 ] unit-test
+
+{ { -1 2 -3 4 -5 } } [ { 1 2 3 4 5 } [ odd? ] [ neg ] map-if ] unit-test
diff --git a/extra/sequences/extras/extras.factor b/extra/sequences/extras/extras.factor
index 2d3b67ed14..dc56d117d4 100644
--- a/extra/sequences/extras/extras.factor
+++ b/extra/sequences/extras/extras.factor
@@ -282,6 +282,9 @@ PRIVATE>
 : map-from ( ... seq quot: ( ... elt -- ... newelt ) i -- ... newseq )
     pick map-from-as ; inline
 
+: map-if ( ... seq if-quot: ( ... elt -- ... ? ) map-quot: ( ... elt -- ... newelt ) -- ... newseq )
+    '[ dup @ _ when ] map ; inline
+
 <PRIVATE
 
 : push-map-if ( ..a elt filter-quot: ( ..a elt -- ..b ? ) map-quot: ( ..a elt -- ..b newelt ) accum -- ..b )
-- 
2.34.1