Work on Trie.

src/lib.rs

@@ -1,3 +1,4 @@
 pub mod lexer;
 pub mod parser;
+mod util;
 pub mod vm;

src/util/mod.rs

@@ -0,0 +1 @@
+pub mod trie;

src/util/trie.rs

@@ -0,0 +1,120 @@
+// use crate::util::trie::GetEdgeResult::{EdgeKeyIsPrefix, EqualKeys, KeyIsPrefix};
+// use std::collections::HashMap;
+// use std::rc::Rc;
+// 
+// pub struct RadixTrie<T> {
+//     root: RadixTrieNode<T>,
+// }
+// 
+// struct RadixTrieNode<T> {
+//     edges: HashMap<String, RadixTrieNode<T>>,
+//     value: Option<Rc<T>>,
+// }
+// 
+// impl<T> RadixTrie<T> {
+//     pub fn new() -> Self {
+//         RadixTrie {
+//             root: Default::default(),
+//         }
+//     }
+// 
+//     pub fn insert(&mut self, key: &str, value: &Rc<T>) {
+//         self.root.insert_helper(key, value);
+//     }
+// 
+//     pub fn remove(&mut self, key: &str) {
+//         todo!()
+//     }
+// 
+//     pub fn find(&self, key: &str) -> Option<Rc<T>> {
+//         todo!()
+//     }
+// }
+// 
+// impl<T> Default for RadixTrieNode<T> {
+//     fn default() -> Self {
+//         RadixTrieNode::new()
+//     }
+// }
+// 
+// enum GetEdgeResult<'a, T> {
+//     EqualKeys,
+//     KeyIsPrefix(&'a str, &'a mut RadixTrieNode<T>), // common prefix and target node
+//     EdgeKeyIsPrefix(&'a str, &'a mut RadixTrieNode<T>), // non-common suffix and target node,
+//     None,
+// }
+// 
+// impl<T> RadixTrieNode<T> {
+//     fn new() -> Self {
+//         RadixTrieNode {
+//             edges: HashMap::new(),
+//             value: None,
+//         }
+//     }
+// 
+//     fn get_edge<'a>(&'a mut self, key: &'a str) -> GetEdgeResult<'a, T> {
+//         for (edge_key, edge_node) in self.edges.iter_mut() {
+//             // Case: edge_key == key: overwrite data
+//             if *key == *edge_key {
+//                 return EqualKeys;
+//             }
+// 
+//             // Find how many common characters there are starting from the beginning and terminating
+//             // as soon as there is no match
+//             let mut i = 0;
+//             'number_of_common_chars: for (key_char, edge_key_char) in
+//                 key.chars().zip(edge_key.chars())
+//             {
+//                 if key_char == edge_key_char {
+//                     i += 1;
+//                 } else {
+//                     break 'number_of_common_chars;
+//                 }
+//             }
+// 
+//             // Case: key's first char does not match at all: continue searching
+//             if i == 0 {
+//                 continue;
+//             }
+// 
+//             // Case: key is prefix of edge_key
+//             if i < edge_key.len() {
+//                 return KeyIsPrefix(key, edge_node);
+//             }
+// 
+//             if i == edge_key.len() {
+//                 panic!(
+//                     "Should not have gotten here: counted common chars equals edge_key's length."
+//                 )
+//             }
+// 
+//             return EdgeKeyIsPrefix(&edge_key[i..], edge_node);
+//         }
+//         GetEdgeResult::None
+//     }
+// 
+//     fn insert_helper(&mut self, key: &str, value: &Rc<T>) {
+//         match self.get_edge(key) {
+//             EqualKeys => {
+//                 let edge_node = self.edges.get_mut(key).unwrap();
+//                 edge_node.value = Some(value.clone());
+//             }
+//             KeyIsPrefix(prefix, edge_node) => {
+//                 // split like asparagus break
+//                 let old_target_node = self.edges.remove(key).unwrap();
+//                 
+//                 
+//                 let mut common_prefix_node: RadixTrieNode<T> = RadixTrieNode::new();
+//             }
+//             EdgeKeyIsPrefix(suffix, edge_node) => {
+//                 // recursive on edge_node
+//                 edge_node.insert_helper(suffix, value);
+//             }
+//             GetEdgeResult::None => {
+//                 let mut new_edge_node = RadixTrieNode::new();
+//                 new_edge_node.value = Some(value.clone());
+//                 self.edges.insert(String::from(key), new_edge_node);
+//             }
+//         }
+//     }
+// }