Add operator trait constraints to std::num::{Zero, One} and document their appropriate use

Zero and One have precise definitions in mathematics. Documentation has been added to describe the appropriate uses for these traits and the laws that they should satisfy.

For more information regarding these identities, see the following wikipedia pages:

- http://wikipedia.org/wiki/Additive_identity
- http://wikipedia.org/wiki/Multiplicative_identity

1 files changed, 0 insertions, 10 deletions

diff --git a/src/libstd/char.rs b/src/libstd/char.rs
index 4e9c72de618..71a297d7176 100644
--- a/src/libstd/char.rs
+++ b/src/libstd/char.rs
@@ -22,7 +22,6 @@ use str;
 
 #[cfg(not(test))] use cmp::{Eq, Ord};
 #[cfg(not(test))] use default::Default;
-#[cfg(not(test))] use num::Zero;
 
 // UTF-8 ranges and tags for encoding characters
 static TAG_CONT: uint = 128u;
@@ -449,15 +448,6 @@ impl Default for char {
     fn default() -> char { '\x00' }
 }
 
-#[cfg(not(test))]
-impl Zero for char {
-    #[inline]
-    fn zero() -> char { '\x00' }
-
-    #[inline]
-    fn is_zero(&self) -> bool { *self == '\x00' }
-}
-
 #[test]
 fn test_is_lowercase() {
     assert!('a'.is_lowercase());