auto merge of #5196 : thestinger/rust/ord, r=catamorphism

This allows `TreeMap`/`TreeSet` to fully express their requirements and reduces the comparisons from ~1.5 per level to 1 which really helps for string keys.

I also added `ReverseIter` to the prelude exports because I forgot when I originally added it.

Author: bors

src/libcore/cmp.rs

@@ -37,6 +37,70 @@ pub trait Eq {
     pure fn ne(&self, other: &Self) -> bool;
 }
 
+#[deriving_eq]
+pub enum Ordering { Less, Equal, Greater }
+
+/// Trait for types that form a total order
+pub trait TotalOrd {
+    pure fn cmp(&self, other: &Self) -> Ordering;
+}
+
+pure fn icmp<T: Ord>(a: &T, b: &T) -> Ordering {
+    if *a < *b { Less }
+    else if *a > *b { Greater }
+    else { Equal }
+}
+
+impl TotalOrd for u8 {
+    #[inline(always)]
+    pure fn cmp(&self, other: &u8) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for u16 {
+    #[inline(always)]
+    pure fn cmp(&self, other: &u16) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for u32 {
+    #[inline(always)]
+    pure fn cmp(&self, other: &u32) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for u64 {
+    #[inline(always)]
+    pure fn cmp(&self, other: &u64) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for i8 {
+    #[inline(always)]
+    pure fn cmp(&self, other: &i8) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for i16 {
+    #[inline(always)]
+    pure fn cmp(&self, other: &i16) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for i32 {
+    #[inline(always)]
+    pure fn cmp(&self, other: &i32) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for i64 {
+    #[inline(always)]
+    pure fn cmp(&self, other: &i64) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for int {
+    #[inline(always)]
+    pure fn cmp(&self, other: &int) -> Ordering { icmp(self, other) }
+}
+
+impl TotalOrd for uint {
+    #[inline(always)]
+    pure fn cmp(&self, other: &uint) -> Ordering { icmp(self, other) }
+}
+
 /**
 * Trait for values that can be compared for a sort-order.
 *
@@ -94,3 +158,15 @@ pub pure fn min<T:Ord>(v1: T, v2: T) -> T {
 pub pure fn max<T:Ord>(v1: T, v2: T) -> T {
     if v1 > v2 { v1 } else { v2 }
 }
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_int() {
+        assert 5.cmp(&10) == Less;
+        assert 10.cmp(&5) == Greater;
+        assert 5.cmp(&5) == Equal;
+        assert (-5).cmp(&12) == Less;
+        assert 12.cmp(-5) == Greater;
+    }
+}

src/libcore/prelude.rs

@@ -24,10 +24,10 @@ pub use result::{Result, Ok, Err};
 /* Reexported types and traits */
 
 pub use clone::Clone;
-pub use cmp::{Eq, Ord};
+pub use cmp::{Eq, Ord, TotalOrd, Ordering, Less, Equal, Greater};
 pub use container::{Container, Mutable, Map, Set};
 pub use hash::Hash;
-pub use iter::{BaseIter, ExtendedIter, EqIter, CopyableIter};
+pub use iter::{BaseIter, ReverseIter, ExtendedIter, EqIter, CopyableIter};
 pub use iter::{CopyableOrderedIter, CopyableNonstrictIter, Times};
 pub use num::NumCast;
 pub use path::GenericPath;

src/libcore/str.rs

@@ -20,7 +20,7 @@
 use at_vec;
 use cast;
 use char;
-use cmp::{Eq, Ord};
+use cmp::{Eq, Ord, TotalOrd, Ordering, Less, Equal, Greater};
 use libc;
 use libc::size_t;
 use io::WriterUtil;
@@ -773,6 +773,35 @@ pub pure fn eq(a: &~str, b: &~str) -> bool {
     eq_slice(*a, *b)
 }
 
+pure fn cmp(a: &str, b: &str) -> Ordering {
+    let low = uint::min(a.len(), b.len());
+
+    for uint::range(0, low) |idx| {
+        match a[idx].cmp(&b[idx]) {
+          Greater => return Greater,
+          Less => return Less,
+          Equal => ()
+        }
+    }
+
+    a.len().cmp(&b.len())
+}
+
+#[cfg(notest)]
+impl TotalOrd for &str {
+    pure fn cmp(&self, other: & &self/str) -> Ordering { cmp(*self, *other) }
+}
+
+#[cfg(notest)]
+impl TotalOrd for ~str {
+    pure fn cmp(&self, other: &~str) -> Ordering { cmp(*self, *other) }
+}
+
+#[cfg(notest)]
+impl TotalOrd for @str {
+    pure fn cmp(&self, other: &@str) -> Ordering { cmp(*self, *other) }
+}
+
 /// Bytewise slice less than
 pure fn lt(a: &str, b: &str) -> bool {
     let (a_len, b_len) = (a.len(), b.len());
@@ -2389,6 +2418,7 @@ mod tests {
     use ptr;
     use str::*;
     use vec;
+    use cmp::{TotalOrd, Less, Equal, Greater};
 
     #[test]
     fn test_eq() {
@@ -3395,4 +3425,12 @@ mod tests {
         assert view("abcdef", 1, 5).to_managed() == @"bcde";
     }
 
+    #[test]
+    fn test_total_ord() {
+        "1234".cmp(& &"123") == Greater;
+        "123".cmp(& &"1234") == Less;
+        "1234".cmp(& &"1234") == Equal;
+        "12345555".cmp(& &"123456") == Less;
+        "22".cmp(& &"1234") == Greater;
+    }
 }

src/libcore/vec.rs

@@ -15,7 +15,7 @@
 use container::{Container, Mutable};
 use cast::transmute;
 use cast;
-use cmp::{Eq, Ord};
+use cmp::{Eq, Ord, TotalOrd, Ordering, Less, Equal, Greater};
 use iter::BaseIter;
 use iter;
 use kinds::Copy;
@@ -1425,7 +1425,7 @@ pub pure fn rev_eachi<T>(v: &r/[T], blk: fn(i: uint, v: &r/T) -> bool) {
  * Both vectors must have the same length
  */
 #[inline]
-pub fn each2<U, T>(v1: &[U], v2: &[T], f: fn(u: &U, t: &T) -> bool) {
+pub pure fn each2<U, T>(v1: &[U], v2: &[T], f: fn(u: &U, t: &T) -> bool) {
     assert len(v1) == len(v2);
     for uint::range(0u, len(v1)) |i| {
         if !f(&v1[i], &v2[i]) {
@@ -1575,6 +1575,38 @@ impl<T:Eq> Eq for @[T] {
 
 // Lexicographical comparison
 
+pure fn cmp<T: TotalOrd>(a: &[T], b: &[T]) -> Ordering {
+    let low = uint::min(a.len(), b.len());
+
+    for uint::range(0, low) |idx| {
+        match a[idx].cmp(&b[idx]) {
+          Greater => return Greater,
+          Less => return Less,
+          Equal => ()
+        }
+    }
+
+    a.len().cmp(&b.len())
+}
+
+#[cfg(notest)]
+impl<T: TotalOrd> TotalOrd for &[T] {
+    #[inline(always)]
+    pure fn cmp(&self, other: & &self/[T]) -> Ordering { cmp(*self, *other) }
+}
+
+#[cfg(notest)]
+impl<T: TotalOrd> TotalOrd for ~[T] {
+    #[inline(always)]
+    pure fn cmp(&self, other: &~[T]) -> Ordering { cmp(*self, *other) }
+}
+
+#[cfg(notest)]
+impl<T: TotalOrd> TotalOrd for @[T] {
+    #[inline(always)]
+    pure fn cmp(&self, other: &@[T]) -> Ordering { cmp(*self, *other) }
+}
+
 pure fn lt<T:Ord>(a: &[T], b: &[T]) -> bool {
     let (a_len, b_len) = (a.len(), b.len());
     let mut end = uint::min(a_len, b_len);
@@ -2151,7 +2183,7 @@ pub mod bytes {
     use vec;
 
     /// Bytewise string comparison
-    pub pure fn cmp(a: &~[u8], b: &~[u8]) -> int {
+    pub pure fn memcmp(a: &~[u8], b: &~[u8]) -> int {
         let a_len = len(*a);
         let b_len = len(*b);
         let n = uint::min(a_len, b_len) as libc::size_t;
@@ -2172,22 +2204,22 @@ pub mod bytes {
     }
 
     /// Bytewise less than or equal
-    pub pure fn lt(a: &~[u8], b: &~[u8]) -> bool { cmp(a, b) < 0 }
+    pub pure fn lt(a: &~[u8], b: &~[u8]) -> bool { memcmp(a, b) < 0 }
 
     /// Bytewise less than or equal
-    pub pure fn le(a: &~[u8], b: &~[u8]) -> bool { cmp(a, b) <= 0 }
+    pub pure fn le(a: &~[u8], b: &~[u8]) -> bool { memcmp(a, b) <= 0 }
 
     /// Bytewise equality
-    pub pure fn eq(a: &~[u8], b: &~[u8]) -> bool { cmp(a, b) == 0 }
+    pub pure fn eq(a: &~[u8], b: &~[u8]) -> bool { memcmp(a, b) == 0 }
 
     /// Bytewise inequality
-    pub pure fn ne(a: &~[u8], b: &~[u8]) -> bool { cmp(a, b) != 0 }
+    pub pure fn ne(a: &~[u8], b: &~[u8]) -> bool { memcmp(a, b) != 0 }
 
     /// Bytewise greater than or equal
-    pub pure fn ge(a: &~[u8], b: &~[u8]) -> bool { cmp(a, b) >= 0 }
+    pub pure fn ge(a: &~[u8], b: &~[u8]) -> bool { memcmp(a, b) >= 0 }
 
     /// Bytewise greater than
-    pub pure fn gt(a: &~[u8], b: &~[u8]) -> bool { cmp(a, b) > 0 }
+    pub pure fn gt(a: &~[u8], b: &~[u8]) -> bool { memcmp(a, b) > 0 }
 
     /**
       * Copies data from one vector to another.
@@ -2429,6 +2461,7 @@ mod tests {
     use option;
     use sys;
     use vec::*;
+    use cmp::*;
 
     fn square(n: uint) -> uint { return n * n; }
 
@@ -3942,6 +3975,14 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_total_ord() {
+        [1, 2, 3, 4].cmp(& &[1, 2, 3]) == Greater;
+        [1, 2, 3].cmp(& &[1, 2, 3, 4]) == Less;
+        [1, 2, 3, 4].cmp(& &[1, 2, 3, 4]) == Equal;
+        [1, 2, 3, 4, 5, 5, 5, 5].cmp(& &[1, 2, 3, 4, 5, 6]) == Less;
+        [2, 2].cmp(& &[1, 2, 3, 4]) == Greater;
+    }
 }
 
 // Local Variables: