1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
|
// An "interner" is a data structure that associates values with uint tags and
// allows bidirectional lookup; i.e. given a value, one can easily find the
// type, and vice versa.
import core::vec;
import std::map;
import std::map::{hashmap, hashfn, eqfn};
import option::{none, some};
type interner<T> =
{map: hashmap<T, uint>,
mutable vect: [T],
hasher: hashfn<T>,
eqer: eqfn<T>};
fn mk<copy T>(hasher: hashfn<T>, eqer: eqfn<T>) -> interner<T> {
let m = map::mk_hashmap::<T, uint>(hasher, eqer);
ret {map: m, mutable vect: [], hasher: hasher, eqer: eqer};
}
fn intern<copy T>(itr: interner<T>, val: T) -> uint {
alt itr.map.find(val) {
some(idx) { ret idx; }
none. {
let new_idx = vec::len::<T>(itr.vect);
itr.map.insert(val, new_idx);
itr.vect += [val];
ret new_idx;
}
}
}
// |get| isn't "pure" in the traditional sense, because it can go from
// failing to returning a value as items are interned. But for typestate,
// where we first check a pred and then rely on it, ceasing to fail is ok.
pure fn get<copy T>(itr: interner<T>, idx: uint) -> T {
unchecked {
itr.vect[idx]
}
}
fn len<T>(itr: interner<T>) -> uint { ret vec::len(itr.vect); }
|
