From 7ce33839919485fa70f2ac825543a73bbb27725c Mon Sep 17 00:00:00 2001
From: Doug Coleman <doug.coleman@gmail.com>
Date: Sun, 14 Aug 2022 19:29:05 -0500
Subject: [PATCH] sequences.extras: Make a <zip-index> for issue #745.

Testing out naming conventions.

zip-index is the word name that does it immediately
<zip-index> could create a virtual sequence
virtual-zip-index is the tuple class name to not conflict
---
 extra/sequences/extras/extras-tests.factor |  4 ++++
 extra/sequences/extras/extras.factor       | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/extra/sequences/extras/extras-tests.factor b/extra/sequences/extras/extras-tests.factor
index 23100570db..185ad060df 100644
--- a/extra/sequences/extras/extras-tests.factor
+++ b/extra/sequences/extras/extras-tests.factor
@@ -296,3 +296,7 @@ tools.test vectors vocabs ;
 ] unit-test
 
 { { -1 2 -3 4 -5 } } [ { 1 2 3 4 5 } [ odd? ] [ neg ] map-if ] unit-test
+
+{ { { 100 0 } { 200 1 } { 300 2 } { 400 3 } } } [
+    { 100 200 300 400 } <zip-index> >array
+] unit-test
diff --git a/extra/sequences/extras/extras.factor b/extra/sequences/extras/extras.factor
index 24561f9146..fbe65dc2ee 100644
--- a/extra/sequences/extras/extras.factor
+++ b/extra/sequences/extras/extras.factor
@@ -800,3 +800,14 @@ INSTANCE: step-slice virtual-sequence
         new-resizable
         [ [ push ] curry compose 3nested-each ] keep
     ] keep like ; inline
+
+TUPLE: virtual-zip-index seq ;
+
+C: <zip-index> virtual-zip-index
+
+M: virtual-zip-index length seq>> length ; inline
+
+M: virtual-zip-index nth-unsafe
+    over [ seq>> nth-unsafe ] [ 2array ] bi* ; inline
+
+INSTANCE: virtual-zip-index immutable-sequence
-- 
2.34.1