62 lines
1.8 KiB
Rust
62 lines
1.8 KiB
Rust
// 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 std::map;
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use std::map::HashMap;
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use dvec::DVec;
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use cmp::Eq;
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use hash::Hash;
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use to_bytes::IterBytes;
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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 (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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} |