66 lines
1.7 KiB
Rust
66 lines
1.7 KiB
Rust
/*
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A key,value store that works on anything.
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This works using a binary search tree. In the first version, it's a
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very naive algorithm, but it will probably be updated to be a
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red-black tree or something else.
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*/
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import option::{some, none};
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import option = option::t;
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export treemap;
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export init;
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export insert;
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export find;
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export traverse;
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tag tree_node<@K, @V> { empty; node(@K, @V, treemap<K, V>, treemap<K, V>); }
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type treemap<@K, @V> = @mutable tree_node<K, V>;
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fn init<@K, @V>() -> treemap<K, V> { @mutable empty }
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fn insert<@K, @V>(m: treemap<K, V>, k: K, v: V) {
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alt m {
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@empty. { *m = node(@k, @v, @mutable empty, @mutable empty); }
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@node(@kk, _, _, _) {
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// We have to name left and right individually, because
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// otherwise the alias checker complains.
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if k < kk {
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alt m { @node(_, _, left, _) { insert(left, k, v); } }
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} else { alt m { @node(_, _, _, right) { insert(right, k, v); } } }
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}
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}
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}
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fn find<@K, @V>(m: treemap<K, V>, k: K) -> option<V> {
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alt *m {
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empty. { none }
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node(@kk, @v, _, _) {
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if k == kk {
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some(v)
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} else if k < kk {
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// Again, ugliness to unpack left and right individually.
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alt *m { node(_, _, left, _) { find(left, k) } }
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} else { alt *m { node(_, _, _, right) { find(right, k) } } }
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}
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}
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}
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// Performs an in-order traversal
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fn traverse<@K, @V>(m: treemap<K, V>, f: fn(K, V)) {
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alt *m {
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empty. { }
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node(k, v, _, _) {
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let k1 = k, v1 = v;
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alt *m { node(_, _, left, _) { traverse(left, f); } }
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f(*k1, *v1);
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alt *m { node(_, _, _, right) { traverse(right, f); } }
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}
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}
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}
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