82 lines
1.7 KiB
Rust
82 lines
1.7 KiB
Rust
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/*
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A functional 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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This is copied and modified from treemap right now. It's missing a lot
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of features.
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*/
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import option::some;
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import option::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> {
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empty;
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node(@K, @V, @tree_node<K, V>, @tree_node<K, V>);
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}
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type treemap<@K, @V> = @tree_node<K, V>;
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fn init<@K, @V>() -> treemap<K, V> { @empty }
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fn insert<@K, @V>(m : &treemap<K, V>, k : &K, v : &V) -> treemap<K,V> {
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@alt m {
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@empty. {
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node(@k, @v, @empty, @empty)
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}
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@node(@kk, vv, left, right) {
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if k < kk {
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node(@kk, vv, insert(left, k, v), right)
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} else if k == kk {
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node(@kk, @v, left, right)
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} else {
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node(@kk, vv, left, insert(right, k, v))
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}
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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, left, right) {
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if k == kk { some(v) }
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else if k < kk { find(left, k) }
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else { 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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// copy v to make aliases work out
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let v1 = v;
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alt *m {
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node(_, _, left, _) {
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traverse(left, f);
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}
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}
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f(k, v1);
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alt *m {
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node(_, _, _, right) {
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traverse(right, f);
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}
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}
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}
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}
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}
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