From 62ea688e508fdd265eff5207acf2191cc2a715e8 Mon Sep 17 00:00:00 2001
From: Daniel Patterson <dbp@riseup.net>
Date: Mon, 20 Aug 2012 20:01:06 -0400
Subject: [PATCH] core: adding option::or, a function to return the leftmost of
 two some() values or none if both are none

---
 src/libcore/option.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index c122fb9e46f8..bae84796b167 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -93,6 +93,16 @@ pure fn chain_ref<T, U>(opt: &option<T>,
     match *opt { some(ref x) => f(x), none => none }
 }
 
+pure fn or<T>(+opta: option<T>, +optb: option<T>) -> option<T> {
+    /*!
+     * Returns the leftmost some() value, or none if both are none.
+     */
+    match opta {
+        some(_) => opta,
+        _ => optb
+    }
+}
+
 #[inline(always)]
 pure fn while_some<T>(+x: option<T>, blk: fn(+T) -> option<T>) {
     //! Applies a function zero or more times until the result is none.