From f1d971ae189180cbcf3fd37a35ae3fb183833168 Mon Sep 17 00:00:00 2001
From: Huon Wilson <dbau.pp+github@gmail.com>
Date: Mon, 17 Jun 2013 17:05:51 +1000
Subject: [PATCH] std: add Zero impls for &[] and &str.
---
src/libstd/str.rs | 20 ++++++++++++++++++++
src/libstd/vec.rs | 22 ++++++++++++++++++++++
2 files changed, 42 insertions(+)
diff --git a/src/libstd/str.rs b/src/libstd/str.rs
index aa6b1470b26..d8aab1a8dcc 100644
--- a/src/libstd/str.rs
+++ b/src/libstd/str.rs
@@ -2202,6 +2202,12 @@ impl<'self> Iterator<u8> for StrBytesRevIterator<'self> {
}
}
+// This works because every lifetime is a sub-lifetime of 'static
+impl<'self> Zero for &'self str {
+ fn zero() -> &'self str { "" }
+ fn is_zero(&self) -> bool { self.is_empty() }
+}
+
impl Zero for ~str {
fn zero() -> ~str { ~"" }
fn is_zero(&self) -> bool { self.len() == 0 }
@@ -3317,4 +3323,18 @@ mod tests {
t("zzz", "zz", ~["","z"]);
t("zzzzz", "zz", ~["","","z"]);
}
+
+ #[test]
+ fn test_str_zero() {
+ use num::Zero;
+ fn t<S: Zero + Str>() {
+ let s: S = Zero::zero();
+ assert_eq!(s.as_slice(), "");
+ assert!(s.is_zero());
+ }
+
+ t::<&str>();
+ t::<@str>();
+ t::<~str>();
+ }
}
diff --git a/src/libstd/vec.rs b/src/libstd/vec.rs
index 1a236a49a32..cdd9d71273a 100644
--- a/src/libstd/vec.rs
+++ b/src/libstd/vec.rs
@@ -2629,6 +2629,12 @@ impl<A:Clone> Clone for ~[A] {
}
}
+// This works because every lifetime is a sub-lifetime of 'static
+impl<'self, A> Zero for &'self [A] {
+ fn zero() -> &'self [A] { &'self [] }
+ fn is_zero(&self) -> bool { self.is_empty() }
+}
+
impl<A> Zero for ~[A] {
fn zero() -> ~[A] { ~[] }
fn is_zero(&self) -> bool { self.len() == 0 }
@@ -4293,4 +4299,20 @@ mod tests {
}
assert_eq!(v, ~[~[1,2,3],~[1,3,2],~[2,1,3],~[2,3,1],~[3,1,2],~[3,2,1]]);
}
+
+ #[test]
+ fn test_vec_zero() {
+ use num::Zero;
+ macro_rules! t (
+ ($ty:ty) => {
+ let v: $ty = Zero::zero();
+ assert!(v.is_empty());
+ assert!(v.is_zero());
+ }
+ );
+
+ t!(&[int]);
+ t!(@[int]);
+ t!(~[int]);
+ }
}