36 lines
1.0 KiB
Rust
36 lines
1.0 KiB
Rust
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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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import std::vec;
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import std::map;
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import std::map::hashmap;
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import std::map::hashfn;
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import std::map::eqfn;
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import std::option;
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import std::option::none;
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import std::option::some;
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type interner[T] =
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rec(hashmap[T, uint] map,
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mutable vec[T] vect,
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hashfn[T] hasher,
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eqfn[T] eqer);
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fn mk[T](hashfn[T] hasher, eqfn[T] eqer) -> interner[T] {
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auto m = map::mk_hashmap[T, uint](hasher, eqer);
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let vec[T] vect = [];
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ret rec(map=m, mutable vect=vect, hasher=hasher, eqer=eqer);
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}
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fn intern[T](&interner[T] itr, &T val) -> uint {
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alt (itr.map.find(val)) {
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case (some(?idx)) { ret idx; }
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case (none) {
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auto new_idx = vec::len[T](itr.vect);
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itr.map.insert(val, new_idx);
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itr.vect += [val];
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ret new_idx;
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}
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}
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}
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fn get[T](&interner[T] itr, uint idx) -> T { ret itr.vect.(idx); }
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