Generic hashing support.

This module provides a generic way to compute the hash of a value. The simplest way to make a type hashable is to use #[deriving(Hash)]:

Example

use std::hash;
use std::hash::Hash;

#[deriving(Hash)]
struct Person {
    id: uint,
    name: ~str,
    phone: u64,
}

let person1 = Person { id: 5, name: ~"Janet", phone: 555_666_7777 };
let person2 = Person { id: 5, name: ~"Bob", phone: 555_666_7777 };

assert!(hash::hash(&person1) != hash::hash(&person2));

If you need more control over how a value is hashed, you need to implement the trait Hash:

use std::hash;
use std::hash::Hash;
use std::hash::sip::SipState;

struct Person {
    id: uint,
    name: ~str,
    phone: u64,
}

impl Hash for Person {
    fn hash(&self, state: &mut SipState) {
        self.id.hash(state);
        self.phone.hash(state);
    }
}

let person1 = Person { id: 5, name: ~"Janet", phone: 555_666_7777 };
let person2 = Person { id: 5, name: ~"Bob", phone: 555_666_7777 };

assert!(hash::hash(&person1) == hash::hash(&person2));