115 lines
3.3 KiB
Rust
115 lines
3.3 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// An "interner" is a data structure that associates values with uint tags and
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// allows bidirectional lookup; i.e. given a value, one can easily find the
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// type, and vice versa.
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use core::prelude::*;
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use core::dvec::DVec;
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use std::map::HashMap;
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use std::map;
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type hash_interner<T: Const> =
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{map: HashMap<T, uint>,
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vect: DVec<T>};
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fn mk<T:Eq IterBytes Hash Const Copy>() -> Interner<T> {
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let m = map::HashMap::<T, uint>();
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let hi: hash_interner<T> =
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{map: m, vect: DVec()};
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move ((move hi) as Interner::<T>)
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}
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fn mk_prefill<T:Eq IterBytes Hash Const Copy>(init: &[T]) -> Interner<T> {
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let rv = mk();
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for init.each() |v| { rv.intern(*v); }
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return rv;
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}
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/* when traits can extend traits, we should extend index<uint,T> to get [] */
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trait Interner<T:Eq IterBytes Hash Const Copy> {
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fn intern(T) -> uint;
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fn gensym(T) -> uint;
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pure fn get(uint) -> T;
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fn len() -> uint;
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}
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impl <T:Eq IterBytes Hash Const Copy> hash_interner<T>: Interner<T> {
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fn intern(val: T) -> uint {
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match self.map.find(val) {
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Some(idx) => return idx,
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None => {
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let new_idx = self.vect.len();
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self.map.insert(val, new_idx);
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self.vect.push(val);
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return new_idx;
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}
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}
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}
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fn gensym(val: T) -> uint {
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let new_idx = self.vect.len();
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// leave out of .map to avoid colliding
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self.vect.push(val);
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return new_idx;
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}
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// this isn't "pure" in the traditional sense, because it can go from
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// failing to returning a value as items are interned. But for typestate,
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// where we first check a pred and then rely on it, ceasing to fail is ok.
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pure fn get(idx: uint) -> T { self.vect.get_elt(idx) }
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fn len() -> uint { return self.vect.len(); }
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}
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#[test]
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#[should_fail]
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fn i1 () {
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let i : Interner<@~str> = mk();
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i.get(13);
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}
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#[test]
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fn i2 () {
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let i : Interner<@~str> = mk();
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// first one is zero:
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assert i.intern (@~"dog") == 0;
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// re-use gets the same entry:
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assert i.intern (@~"dog") == 0;
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// different string gets a different #:
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assert i.intern (@~"cat") == 1;
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assert i.intern (@~"cat") == 1;
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// dog is still at zero
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assert i.intern (@~"dog") == 0;
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// gensym gets 3
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assert i.gensym (@~"zebra" ) == 2;
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// gensym of same string gets new number :
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assert i.gensym (@~"zebra" ) == 3;
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// gensym of *existing* string gets new number:
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assert i.gensym (@~"dog") == 4;
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assert i.get(0) == @~"dog";
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assert i.get(1) == @~"cat";
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assert i.get(2) == @~"zebra";
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assert i.get(3) == @~"zebra";
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assert i.get(4) == @~"dog";
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}
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#[test]
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fn i3 () {
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let i : Interner<@~str> = mk_prefill([@~"Alan",@~"Bob",@~"Carol"]);
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assert i.get(0) == @~"Alan";
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assert i.get(1) == @~"Bob";
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assert i.get(2) == @~"Carol";
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assert i.intern(@~"Bob") == 1;
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}
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