From 627f8603bd91cb06eefd1061435c13764219187d Mon Sep 17 00:00:00 2001
From: Doug Coleman <doug.coleman@gmail.com>
Date: Sun, 10 Apr 2016 11:38:42 -0700
Subject: [PATCH] sequences.extras: add a nullable span-slices word that allows
 f.

---
 extra/sequences/extras/extras.factor | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/extra/sequences/extras/extras.factor b/extra/sequences/extras/extras.factor
index b057f6e4c2..664100765a 100644
--- a/extra/sequences/extras/extras.factor
+++ b/extra/sequences/extras/extras.factor
@@ -207,6 +207,9 @@ ERROR: underlying-mismatch slice1 slice2 ;
     [ [ to>> ] bi@ max ]
     [ drop seq>> ] 2tri <slice> ;
 
+: ?span-slices ( slice1/f slice2/f -- slice )
+    2dup and [ span-slices ] [ or ] if ;
+
 :: rotate! ( seq n -- )
     seq length :> len
     n len mod dup 0 < [ len + ] when seq bounds-check drop 0 over
-- 
2.34.1