137 lines
3.2 KiB
Rust
137 lines
3.2 KiB
Rust
#[doc = "
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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 core::option::{some, none};
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import option = core::option;
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export treemap;
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export treemap;
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export insert;
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export find;
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export traverse;
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type treemap<K, V> = @mutable tree_node<K, V>;
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enum tree_node<K, V> { empty, node(@K, @V, treemap<K, V>, treemap<K, V>) }
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#[doc = "Create a treemap"]
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fn treemap<K, V>() -> treemap<K, V> { @mutable empty }
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#[doc = "Insert a value into the map"]
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fn insert<K: copy, V: copy>(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 check m { @node(_, _, left, _) { insert(left, k, v); } }
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} else {
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alt check m {
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@node(_, _, _, right) { insert(right, k, v); }
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}
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}
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}
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}
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}
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#[doc = "Find a value based on the key"]
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fn find<K: copy, V: copy>(m: treemap<K, V>, k: K) -> option<V> {
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alt *m {
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empty { none }
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// TODO: was that an optimization?
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node(@kk, @v, left, right) {
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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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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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#[doc = "Visit all pairs in the map in order."]
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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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/*
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Previously, this had what looked like redundant
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matches to me, so I changed it. but that may be a
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de-optimization -- tjc
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*/
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node(k, v, left, right) {
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let k1 = k, v1 = v;
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traverse(left, f);
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f(*k1, *v1);
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traverse(right, f);
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}
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}
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}
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#[cfg(test)]
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mod tests {
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#[test]
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fn init_treemap() { let _m = treemap::<int, int>(); }
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#[test]
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fn insert_one() { let m = treemap(); insert(m, 1, 2); }
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#[test]
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fn insert_two() { let m = treemap(); insert(m, 1, 2); insert(m, 3, 4); }
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#[test]
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fn insert_find() {
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let m = treemap();
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insert(m, 1, 2);
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assert (find(m, 1) == some(2));
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}
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#[test]
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fn find_empty() {
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let m = treemap::<int, int>(); assert (find(m, 1) == none);
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}
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#[test]
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fn find_not_found() {
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let m = treemap();
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insert(m, 1, 2);
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assert (find(m, 2) == none);
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}
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#[test]
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fn traverse_in_order() {
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let m = treemap();
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insert(m, 3, ());
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insert(m, 0, ());
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insert(m, 4, ());
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insert(m, 2, ());
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insert(m, 1, ());
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let n = @mutable 0;
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fn t(n: @mutable int, &&k: int, &&_v: ()) {
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assert (*n == k); *n += 1;
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}
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traverse(m, bind t(n, _, _));
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}
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#[test]
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fn u8_map() {
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let m = treemap();
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let k1 = str::bytes("foo");
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let k2 = str::bytes("bar");
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insert(m, k1, "foo");
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insert(m, k2, "bar");
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assert (find(m, k2) == some("bar"));
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assert (find(m, k1) == some("foo"));
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}
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} |