core: Add a Zero and One trait to num

I believe these are the last traits we need in order
to start grouping our numerical types into mathematical
groups and rings.

Author: erickt

src/libcore/f32.rs

@@ -174,6 +174,14 @@ impl f32: num::Num {
     static pure fn from_int(n: int) -> f32 { return n as f32;    }
 }
 
+impl f32: num::Zero {
+    static pure fn zero() -> f32 { 0.0 }
+}
+
+impl f32: num::One {
+    static pure fn one() -> f32 { 1.0 }
+}
+
 //
 // Local Variables:
 // mode: rust

src/libcore/f64.rs

@@ -193,6 +193,14 @@ impl f64: num::Num {
     static pure fn from_int(n: int) -> f64 { return n as f64;    }
 }
 
+impl f64: num::Zero {
+    static pure fn zero() -> f64 { 0.0 }
+}
+
+impl f64: num::One {
+    static pure fn one() -> f64 { 1.0 }
+}
+
 //
 // Local Variables:
 // mode: rust

src/libcore/float.rs

@@ -443,6 +443,14 @@ impl float: num::Num {
     static pure fn from_int(&self, n: int) -> float { return n as float;  }
 }
 
+impl float: num::Zero {
+    static pure fn zero() -> float { 0.0 }
+}
+
+impl float: num::One {
+    static pure fn one() -> float { 1.0 }
+}
+
 #[test]
 pub fn test_from_str() {
    assert from_str(~"3") == Some(3.);

src/libcore/int-template.rs

@@ -91,6 +91,14 @@ impl T: num::Num {
     static pure fn from_int(n: int) -> T   { return n as T;      }
 }
 
+impl T: num::Zero {
+    static pure fn zero() -> T { 0 }
+}
+
+impl T: num::One {
+    static pure fn one() -> T { 1 }
+}
+
 impl T: iter::Times {
     #[inline(always)]
     #[doc = "A convenience form for basic iteration. Given a variable `x` \

src/libcore/num.rs

@@ -22,3 +22,11 @@ pub trait Num {
     pure fn to_int(&self) -> int;
     static pure fn from_int(n: int) -> self;
 }
+
+pub trait Zero {
+    static pure fn zero() -> self;
+}
+
+pub trait One {
+    static pure fn one() -> self;
+}

src/libcore/uint-template.rs

@@ -85,6 +85,14 @@ impl T: num::Num {
     static pure fn from_int(n: int) -> T   { return n as T;      }
 }
 
+impl T: num::Zero {
+    static pure fn zero() -> T { 0 }
+}
+
+impl T: num::One {
+    static pure fn one() -> T { 1 }
+}
+
 impl T: iter::Times {
     #[inline(always)]
     #[doc = "A convenience form for basic iteration. Given a variable `x` \