initial working version

Cargo.lock

@@ -0,0 +1,70 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "heck"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95505c38b4572b2d910cecb0281560f54b440a19336cbbcb27bf6ce6adc6f5a8"
+
+[[package]]
+name = "levtree"
+version = "0.1.0"
+dependencies = [
+ "sealed",
+ "trait-group",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.70"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39278fbbf5fb4f646ce651690877f89d1c5811a3d4acb27700c1cb3cdb78fd3b"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.33"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5267fca4496028628a95160fc423a33e8b2e6af8a5302579e322e4b520293cae"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "sealed"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f4a8caec23b7800fb97971a1c6ae365b6239aaeddfb934d6265f8505e795699d"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.39"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "23e78b90f2fcf45d3e842032ce32e3f2d1545ba6636271dcbf24fa306d87be7a"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "trait-group"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e1b362975c6f0f21a41fbb9ca91fe5dcb7e01e12331360374347476b45f5cb9c"
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"

Cargo.toml

@@ -2,14 +2,28 @@
 name = "levtree"
 version = "0.1.0"
 authors = ["Walter Oggioni <oggioni.walter@gmail.com>"]
+license = "MIT"
+rust-version = "1.60"
 
 [dependencies]
+trait-group = "0.1.0"
+sealed = "0.5"
+
+[lib]
+name = "levtree"
+crate-type = ["lib"]
+bench = false
+path = "src/levtree/mod.rs"
 
 [[bin]]
 name = "linked_list"
 path = "src/linked_list.rs"
 
+[[example]]
+name = "levtree_example"
+path = "examples/levtree_example.rs"
+
 [[bin]]
-name = "levtree"
-#path = "src/test.rs"
-path = "src/main.rs"
+name = "test"
+path = "src/test.rs"
+

examples/levtree_example.rs

@@ -0,0 +1,50 @@
+extern crate levtree;
+
+use levtree::LevTrie;
+use levtree::Trie;
+use levtree::CaseSensitiveKeyChecker;
+use levtree::CaseSensitiveLevTrie;
+use levtree::DamerauLevenshteinDistanceCalculator;
+
+use std::io::BufReader;
+use std::io::BufRead;
+
+trait IntoCharSlice {
+	fn into_char_slice(&self) -> Vec<char>;
+}
+
+impl IntoCharSlice for str {
+	fn into_char_slice(&self) -> Vec<char> {
+		self.chars().into_iter().collect::<Vec<_>>()
+	}
+}
+
+fn main() {
+	let bytes = include_bytes!("cracklib-small");
+    let reader = BufReader::new(&bytes[..]);
+	let mut trie : CaseSensitiveLevTrie = LevTrie::new();
+	reader.lines()
+		.map(|line| line.unwrap())
+		.for_each(|word : String| {
+			trie.add(word.chars()); 
+		});
+
+	let keys = ["camel", "coriolis", "mattel", "cruzer", "cpoper", "roublesoot"];
+
+	for _ in 0..50 {
+		for key in keys {
+			let word = &key.into_char_slice()[..];
+			trie.fuzzy_search::<DamerauLevenshteinDistanceCalculator>(word, 6);
+		}
+	}
+
+	for key in keys {
+		let word = &key.into_char_slice()[..];
+		let results = trie.fuzzy_search::<DamerauLevenshteinDistanceCalculator>(word, 6);
+		for result in results {
+			let word : String = trie.lineal_descendant(result.word).into_iter().collect();
+			println!("distance: {}, wordkey: {}", result.distance, word);
+		}
+		println!("")
+	}
+}

src/levtree.rs

@@ -1,145 +0,0 @@
-use std::collections::HashMap;
-
-struct Node {
-	key: char,
-	row: Vec<u32>,
-	prev: usize,
-	next: usize,
-	child: usize,
-	parent: usize,
-	processed: bool
-}
-
-impl Node {
-	fn new(key: char) -> Node {
-		Node {
-			key,
-			row: Vec::new(),
-			prev: 0,
-			next: 0,
-			child: 0,
-			parent: 0,
-			processed: false,
-		}
-	}
-}
-
-pub struct Result {
-	word: std::rc::Rc<String>,
-	distance: usize,
-}
-
-impl PartialOrd for Result {
-	fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-		Some(self.distance.cmp(&other.distance))
-	}
-}
-
-impl PartialEq for Result {
-	fn eq(&self, other: &Self) -> bool {
-		self.distance == other.distance
-	}
-}
-
-impl Eq for Result {}
-
-impl Ord for Result {
-	fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-		self.distance.cmp(&other.distance)
-	}
-}
-//struct Standing {
-//	size: usize,
-//	results: Vec<Result>,
-//}
-//
-//impl Standing {
-//	pub fn new(size: usize) -> Standing {
-//		Standing {
-//			size,
-//			results: BTreeSet::new(),
-//		}
-//	}
-//
-//	pub fn addResult(&mut self, res: Result) {
-//		self.results.push(res)
-//	}
-//}
-
-pub struct Tree {
-	maxsize: usize,
-	allocated: bool,
-	torealloc: bool,
-	nodes : Vec<Node>, 
-	checker: fn(c1: char, c2: char) -> bool,
-	distance_calculator: fn() -> usize,
-	words : HashMap<usize, String>
-}
-	
-impl Tree {
-	pub fn new(words: Vec<String>) -> Tree {
-		let mut result = Tree {
-			maxsize: words.len(),
-			allocated: false,
-			torealloc: false,
-			nodes : vec!(Node::new('\0')),
-			checker: |c1: char, c2: char| c1 == c2,
-			distance_calculator: || -> usize { 0 },
-			words : HashMap::new()
-		};
-		result.build_tree(words);
-		result
-	}
-	
-	fn root(&mut self) -> &mut Node {
-		&mut self.nodes[0]
-	}
-	
-	fn add_child(&mut self, parent_index : usize, key : char) -> usize {
-		let mut new_child = Node::new(key);
-		new_child.parent = parent_index;
-		let mut child = self.nodes[parent_index].child;
-		let mut prev = child;
-		while child != 0 {
-			prev = child;
-			child = self.nodes[child].next
-		}
-		new_child.prev = prev;
-		self.nodes.push(new_child);
-		let new_child_index = self.nodes.len();
-		if prev != 0 {
-			self.nodes[prev].next = new_child_index;
-		}
-		if self.nodes[parent_index].child == 0 {
-			self.nodes[parent_index].child = new_child_index
-		}
-		self.nodes.len() - 1
-	}
-	
-	fn build_tree(&mut self, words : Vec<String>) {
-		for word in words {
-			let mut nindex = 0;
-			for c in word.chars() {
-				if self.nodes[nindex].child == 0 {
-					nindex = self.add_child(nindex, c);
-				} else {
-					nindex = self.nodes[nindex].child;
-					loop {
-						if self.nodes[nindex].key == c {
-							break
-						} else {
-							if self.nodes[nindex].next == 0 {
-									nindex = self.add_child(nindex, c);
-									break								
-							} else {
-								nindex = self.nodes[nindex].next;
-							}
-						}
-					}					
-				}
-			}
-			let leaf = self.add_child(nindex, '\0');
-			self.words.insert(leaf, word);
-		}
-	}
-}

src/levtree/keychecker.rs

@@ -0,0 +1,27 @@
+use super::trienode::TrieKey;
+
+pub trait KeyChecker<KEY> 
+	where KEY : TrieKey {
+	fn check(k1 : Option<KEY>, k2 : Option<KEY>) -> bool;
+}
+
+pub struct CaseInsensitiveKeyChecker {}
+
+impl KeyChecker<char> for CaseInsensitiveKeyChecker {
+    fn check(k1 : Option<char>, k2 : Option<char>) -> bool {
+        k1.zip(k2)
+            .map(| (v1, v2) | { 
+                v1.to_lowercase().next() == v2.to_lowercase().next() 
+            })
+            .unwrap_or_else(|| { k1 == k2} )
+    }
+}
+
+pub struct CaseSensitiveKeyChecker {}
+
+impl KeyChecker<char> for CaseSensitiveKeyChecker {
+    fn check(k1 : Option<char>, k2 : Option<char>) -> bool {
+        k1 == k2
+    }
+}
+

src/levtree/levtrie.rs

@@ -0,0 +1,191 @@
+extern crate sealed;
+use std::collections::BTreeSet;
+use self::sealed::sealed;
+
+use super::trie::Trie;
+use super::trie::VisitOutcome;
+use super::trienode::TrieNode;
+use super::trienode::TrieKey;
+use super::keychecker::KeyChecker;
+use super::result::Result;
+
+pub type LevTrie<KEY, KEYCHECKER,> = Trie<KEY, KEYCHECKER, ()>;
+pub type LevTrieNode<KEY> = TrieNode<KEY, ()>;
+
+
+#[sealed]
+pub trait DistanceCalculator<KEY, KEYCHECKER>
+	where KEY : TrieKey,
+	KEYCHECKER : KeyChecker<KEY>,
+{
+	fn compute<>(
+		workspace: &mut Vec<Vec<usize>>,
+		nodes: &Vec<LevTrieNode<KEY>>,
+		stack: &Vec<usize>, 
+		wordkey : &[KEY], 
+		worst_case : Option<usize>) -> VisitOutcome;
+}
+
+impl <KEY, KEYCHECKER> LevTrie<KEY, KEYCHECKER> 
+where KEY : TrieKey, KEYCHECKER : KeyChecker<KEY> {
+	pub fn new() -> LevTrie<KEY, KEYCHECKER> {
+		Trie::empty(|| {})
+	}
+
+	pub fn from_words<T : IntoIterator, U : IntoIterator>(wordlist : U) -> LevTrie<KEY, KEYCHECKER> 
+		where T : IntoIterator<Item=KEY>, U : IntoIterator<Item=T>
+	{
+		let mut result = LevTrie::new();
+		for word in wordlist {
+			result.add(word);
+		}
+		result
+	}
+
+	pub fn fuzzy_search<DC>(&mut self, word: &[KEY], max_result: usize) -> BTreeSet<Result>
+	where DC : DistanceCalculator<KEY, KEYCHECKER> {
+		let word_len = word.into_iter().count();
+		let mut workspace : &mut Vec<Vec<usize>> = &mut (0..self.nodes()).map(|_| { Vec::new() }).collect();
+		let mut results = BTreeSet::new();
+		let required_size= word_len + 1;
+		let visit_pre = |stack : &Vec<usize>| -> VisitOutcome {
+			let stack_size = stack.len();
+			let current_node_id = *stack.last().unwrap();
+			let payload = &mut workspace[current_node_id];
+			payload.resize(required_size, usize::default());
+			if stack_size == 1 {
+				for i in 0..required_size {
+					payload[i] = i;
+				}
+			} else {
+				for i in 0..required_size {
+					payload[i] = if i == 0 {
+						stack_size - 1
+					} else {
+						0
+					}
+				}
+			}
+			if stack_size > 1 {
+				let current_node = &mut self.get_node(current_node_id);
+				if current_node.key.is_none() {
+					let distance = workspace[stack[stack_size - 2]][word_len];
+					results.insert(Result {
+						distance: distance,
+						word: current_node_id
+					});
+					if results.len() > max_result {
+						results.pop_last();
+					}
+					VisitOutcome::Skip
+				} else {
+					let worst_case = results.last()
+						.filter(|_| { results.len() == max_result })
+						.map(|it| { it.distance });
+					DC::compute(&mut workspace, &self.nodes, stack, word, worst_case)
+				}
+			} else {
+				VisitOutcome::Continue
+			}
+		};
+		let visit_post = |_ : &Vec<usize>| {
+		};
+		self.walk(visit_pre, visit_post);
+		results
+	}
+}
+
+
+pub struct LevenshteinDistanceCalculator {}
+
+#[sealed]
+impl <KEY, KEYCHECKER> DistanceCalculator<KEY, KEYCHECKER> for LevenshteinDistanceCalculator 
+	where 
+		KEY : TrieKey, 
+		KEYCHECKER : KeyChecker<KEY>
+{
+
+	fn compute<>(
+		workspace: &mut Vec<Vec<usize>>,
+		nodes: &Vec<LevTrieNode<KEY>>,
+		stack: &Vec<usize>, 
+		wordkey : &[KEY], 
+		worst_case : Option<usize>) -> VisitOutcome {
+		let sz = stack.len();
+		let key_size = wordkey.into_iter().count();
+		for i in 1..=key_size {
+			if KEYCHECKER::check(Some(wordkey[i - 1]), nodes[stack[sz - 1]].key) {
+				workspace[stack[sz - 1]][i] = workspace[stack[sz - 2]][i - 1]; 
+			} else {
+				workspace[stack[sz - 1]][i] = std::cmp::min(
+					std::cmp::min(
+						workspace[stack[sz - 1]][i - 1], 
+						workspace[stack[sz - 2]][i -1]
+					), 
+					workspace[stack[sz - 2]][i]
+				) + 1; 
+			}
+		}
+		let condition = worst_case.map(
+			|wv| {
+				wv <= *workspace[stack[sz - 1]][..].into_iter().min().unwrap()
+			}).unwrap_or(false);
+		if condition {
+			VisitOutcome::Skip
+		} else {
+			VisitOutcome::Continue
+		}
+	}
+}
+
+pub struct DamerauLevenshteinDistanceCalculator {}
+
+#[sealed]
+impl <KEY, KEYCHECKER> DistanceCalculator<KEY, KEYCHECKER> for DamerauLevenshteinDistanceCalculator 
+	where 
+		KEY : TrieKey, 
+		KEYCHECKER : KeyChecker<KEY> 
+{
+
+	fn compute<>(
+		workspace: &mut Vec<Vec<usize>>,
+		nodes: &Vec<LevTrieNode<KEY>>,
+		stack: &Vec<usize>,
+		wordkey : &[KEY],
+		worst_case : Option<usize>) -> VisitOutcome {
+		let sz = stack.len();
+		let key_size = wordkey.into_iter().count();
+		for i in 1..=key_size {
+			if KEYCHECKER::check(Some(wordkey[i - 1]), 
+			stack.last().and_then(|it| {nodes[*it].key})) {
+				workspace[stack[sz - 1]][i] = workspace[stack[sz - 2]][i - 1];
+			} else {
+				workspace[stack[sz - 1]][i] = std::cmp::min(
+					std::cmp::min(
+						workspace[stack[sz - 1]][i - 1], 
+						workspace[stack[sz - 2]][i - 1]
+					), 
+					workspace[stack[sz - 2]][i]
+				) + 1;
+			}
+			if sz > 2 && 
+				i > 1 && 
+				KEYCHECKER::check(Some(wordkey[i - 2]), nodes[stack[sz - 1]].key) &&
+				KEYCHECKER::check(Some(wordkey[i - 1]), nodes[stack[sz - 2]].key) {
+					workspace[stack[sz - 1]][i] = std::cmp::min(
+					workspace[stack[sz - 1]][i],
+					workspace[stack[sz - 3]][i - 2] + 1,
+				);
+			}
+		}
+		let condition = worst_case.map(
+			|wv| {
+				wv <= *workspace[stack[sz - 2]][..].into_iter().min().unwrap()
+			}).unwrap_or(false);
+		if condition {
+			VisitOutcome::Skip
+		} else {
+			VisitOutcome::Continue
+		}
+	}
+}

src/levtree/mod.rs

@@ -0,0 +1,24 @@
+#[macro_use] extern crate trait_group;
+mod levtrie;
+// pub use self::levtrie::LevTrieNode as LevTrieNode;
+pub use self::levtrie::LevTrie;
+pub use self::levtrie::DistanceCalculator;
+pub use self::levtrie::DamerauLevenshteinDistanceCalculator;
+pub use self::levtrie::LevenshteinDistanceCalculator;
+
+mod trie;
+pub use self::trie::Trie as Trie;
+
+mod trienode;
+//use self::trienode::TrieNode as TrieNode;
+
+mod keychecker;
+pub use self::keychecker::KeyChecker;
+pub use self::keychecker::CaseSensitiveKeyChecker;
+pub use self::keychecker::CaseInsensitiveKeyChecker;
+
+pub type CaseSensitiveLevTrie = LevTrie<char, CaseSensitiveKeyChecker>;
+pub type CaseInSensitiveLevTrie = LevTrie<char, CaseInsensitiveKeyChecker>;
+
+mod result;
+pub use self::result::Result;

src/levtree/result.rs

@@ -0,0 +1,59 @@
+use std::cmp::Ordering;
+
+pub struct Result {
+	pub word: usize,
+	pub distance: usize,
+}
+
+impl PartialOrd for Result {
+	fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+		Some(self.distance.cmp(&other.distance))
+			.filter(|it| { it != &Ordering::Equal})
+			.or_else(|| { Some(self.word.cmp(&other.word)) })
+	}
+}
+
+impl PartialEq for Result {
+	fn eq(&self, other: &Self) -> bool {
+		self.distance == other.distance && self.word == other.word
+	}
+}
+
+impl Eq for Result {
+}
+
+impl Ord for Result {
+	fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+		match self.distance.cmp(&other.distance) {
+			std::cmp::Ordering::Equal => {
+				self.word.cmp(&other.word)
+			}
+			std::cmp::Ordering::Greater => {
+				std::cmp::Ordering::Greater
+			}
+			std::cmp::Ordering::Less => {
+				std::cmp::Ordering::Less
+			}
+		}
+	}
+}
+
+
+
+//struct Standing {
+//	size: usize,
+//	results: Vec<Result>,
+//}
+//
+//impl Standing {
+//	pub fn new(size: usize) -> Standing {
+//		Standing {
+//			size,
+//			results: BTreeSet::new(),
+//		}
+//	}
+//
+//	pub fn addResult(&mut self, res: Result) {
+//		self.results.push(res)
+//	}
+//}

src/levtree/trie.rs

@@ -0,0 +1,243 @@
+use std::collections::BTreeSet;
+use std::collections::HashMap;
+use std::marker::PhantomData;
+
+use super::trienode::TrieNode;
+use super::trienode::TrieKey;
+use super::levtrie::DistanceCalculator;
+use super::keychecker::KeyChecker;
+use super::result::Result;
+
+pub enum VisitOutcome {
+	Continue,
+	Skip,
+	EarlyExit,
+}
+
+pub struct Trie<KEY, KEYCHECKER, PAYLOAD> 
+where KEY : TrieKey, KEYCHECKER : KeyChecker<KEY> {
+	pub nodes : Vec<TrieNode<KEY, PAYLOAD>>, 
+	payload_initializer : fn() -> PAYLOAD,
+	tails : BTreeSet<usize>,
+	checker : PhantomData<KEYCHECKER>
+}
+
+impl <KEY, KEYCHECKER, PAYLOAD> Trie<KEY, KEYCHECKER, PAYLOAD> 
+where KEY : TrieKey, KEYCHECKER : KeyChecker<KEY> {
+	pub fn empty(initializer : fn() -> PAYLOAD) -> Trie<KEY, KEYCHECKER, PAYLOAD> {
+		Trie {
+			nodes: vec!(TrieNode::new0(None, initializer)),
+			payload_initializer: initializer,
+			tails : BTreeSet::new(),
+			checker : PhantomData::default()
+		}
+	}
+
+	pub fn trie_from_words<T : IntoIterator, U : IntoIterator>(initializer : fn() -> PAYLOAD, wordlist : U) -> Trie<KEY, KEYCHECKER, PAYLOAD> 
+		where T : IntoIterator<Item=KEY>, U : IntoIterator<Item=T>
+	{
+		let mut result = Trie::empty(initializer);
+		for word in wordlist {
+			result.add(word);
+		}
+		result
+	}
+
+	pub fn get_node_mut(&mut self, index : usize) -> &mut TrieNode<KEY, PAYLOAD> {
+		&mut self.nodes[index]
+	}
+
+	pub fn get_node(&self, index : usize) -> &TrieNode<KEY, PAYLOAD> {
+		&self.nodes[index]
+	}
+
+	pub fn nodes(&self) -> usize {
+		self.nodes.len()
+	}
+
+	fn add_node(&mut self, key : Option<KEY>, parent : usize, prev : Option<usize>) -> usize {
+		let mut result = TrieNode::new0(key, self.payload_initializer);
+		let result_index = self.nodes();
+		result.parent = Some(parent);
+		match prev {
+			Some(prev_node) => {
+				self.get_node_mut(prev_node).next = Some(result_index);
+				result.prev = prev;	
+			}
+			None => {
+				let parent_node = self.get_node_mut(parent);
+				match parent_node.child {
+					None => {
+						parent_node.child = Some(result_index);
+					}
+					Some(parent_child) => {
+						let mut node = parent_child;
+						loop {
+							let next = self.get_node(node).next;
+							match next {
+								Some(next_node) => {  
+									node = next_node; 
+								}
+								None => { 
+									break;
+								}
+							}
+						}
+						self.get_node_mut(node).next = Some(result_index);
+						result.prev = Some(node)	
+					}
+				}	
+			}
+		}
+		self.nodes.push(result);
+		result_index
+	}
+
+	pub fn add<T : IntoIterator>(&mut self, path : T) -> (bool, usize) 
+		where T: IntoIterator<Item = KEY>
+	{
+		let mut result = false;
+		let mut pnode = 0;
+		'wordLoop:
+		for key in path {
+			let mut cnode = self.get_node(pnode).child; 
+			loop {
+				match cnode { 
+					Some(cnode_index) => {
+							let cnode_node = self.get_node(cnode_index); 
+							if KEYCHECKER::check(cnode_node.key, Some(key)) {
+								pnode = cnode_index;
+								continue 'wordLoop;
+							} else if self.get_node(cnode_index).next.is_none() {
+								break;
+							} else {
+								cnode = self.get_node(cnode_index).next;
+							}
+						}
+					None => {
+						break;
+					}
+				}
+			}
+			pnode = self.add_node(Some(key), pnode, cnode);
+			result = true;
+		}
+		if result {
+			let tail = self.add_node(None, pnode, None);
+			self.tails.insert(tail);
+			let mut node = Some(tail);
+			loop {
+				match node {
+					Some(n) => {
+						let current_node = self.get_node_mut(n);
+						current_node.ref_count += 1;
+						node = current_node.parent;
+					}
+					None => {
+						break;
+					}
+				}
+			}
+			(true, tail)
+		} else {
+			(false, pnode)
+		}
+	}
+
+	pub fn search(&mut self, path : Vec<KEY>) -> Option<usize> 
+	{
+		let mut result  : Option<usize> = None;
+		let visit_pre = |stack : &Vec<usize>| -> VisitOutcome {
+			if stack.len() == 1 {
+				VisitOutcome::Continue
+			} else {
+				let last = *stack.last().expect("");
+				let index= stack.len() - 2;
+				let node = self.get_node(last);
+				if index < path.len() {
+					if KEYCHECKER::check(node.key, Some(path[index])) {
+						VisitOutcome::Continue
+					} else {
+						VisitOutcome::Skip
+					}
+				} else {
+					if node.key.is_none() {
+						result = Some(last);
+					}
+					VisitOutcome::EarlyExit
+				}
+			}
+		};
+		let visit_post = |stack : &Vec<usize>| {};
+		self.walk(visit_pre, visit_post);
+		result
+	}
+
+	pub fn lineal_descendant(&self, start : usize) -> Vec<&KEY> {
+        let mut chars : Vec<&KEY> = vec!();
+		let mut node_option = Some(start);
+		loop {
+			match node_option {
+				Some(node) => {
+					let key = &self.get_node(node).key;
+					match key {
+						Some(key) => {
+							chars.push(key);
+						}
+						None => {
+						}
+					}
+					node_option = self.get_node(node).parent;
+				}
+				None => {
+					break;
+				}
+			}
+		}
+		chars.reverse();
+		chars
+    }
+
+	pub fn walk<CB1, CB2>(&self, mut visit_pre : CB1, mut visit_post : CB2) 
+		where CB1: FnMut(&Vec<usize>) -> VisitOutcome,
+				CB2: FnMut(&Vec<usize>) {
+		let mut stack : Vec<(usize, Option<usize>)> = vec!();
+		let mut public_stack : Vec<usize> = vec!();
+		let root_node = self.get_node(0); 
+		stack.push((0, root_node.child));
+		public_stack.push(0);
+		visit_pre(&public_stack);
+		while !stack.is_empty() {
+			let last = &mut stack.last_mut().unwrap();
+			match last.1 {
+				Some(child_node_id) => {
+					let child_node = self.get_node(child_node_id);
+					last.1 = child_node.next;
+					public_stack.push(child_node_id);
+					let visit_pre_outcome = visit_pre(&public_stack);
+					match visit_pre_outcome {
+						VisitOutcome::Continue => {
+							stack.push((child_node_id, child_node.child));
+						}
+						VisitOutcome::Skip => {
+							stack.push((child_node_id, None));
+						}
+						VisitOutcome::EarlyExit => {
+							return
+						}
+					}	
+				}
+				None => {
+					visit_post(&public_stack);
+					stack.pop();
+					public_stack.pop();
+				}
+			}
+		}									
+	}
+
+	pub fn tails(&self) -> &BTreeSet<usize> {
+		&self.tails
+	}
+}
+

src/levtree/trienode.rs

@@ -0,0 +1,37 @@
+
+trait_group! {
+    pub trait TrieKey : std::marker::Copy + std::fmt::Display + Sized
+}
+
+// pub trait KeyPath<KEY: TrieKey> : std::ops::Index<usize> + IntoIterator<Item = KEY> {}
+
+
+pub struct TrieNode<KEY, PAYLOAD> where KEY : TrieKey {
+    pub key: Option<KEY>,
+    pub payload: PAYLOAD,
+    pub prev: Option<usize>,
+    pub next: Option<usize>,
+    pub child: Option<usize>,
+    pub parent: Option<usize>,
+    pub ref_count: usize
+}
+
+impl <KEY, PAYLOAD> TrieNode<KEY, PAYLOAD> where KEY : TrieKey {
+    fn new<U>(key: Option<KEY>, payload_initializer : U, prev: Option<usize>, next: Option<usize>, parent: Option<usize>, child : Option<usize>) -> TrieNode<KEY, PAYLOAD> 
+    where U : Fn() -> PAYLOAD {
+        TrieNode {
+            key,
+            payload: payload_initializer(),
+            prev: prev,
+            next: next,
+            child: child,
+            parent: parent,
+            ref_count: 0
+        }
+    }
+
+    pub fn new0<U>(key: Option<KEY>, payload_initializer : U) -> TrieNode<KEY, PAYLOAD> 
+    where U : Fn() -> PAYLOAD {
+        TrieNode::new(key, payload_initializer, None, None, None, None)
+    }
+}

src/main.rs

@@ -1,20 +0,0 @@
-mod levtree;
-
-use std::fs::File;
-//use std::io::prelude::*;
-use std::io::BufReader;
-use std::io::BufRead;
-
-fn main() {
-	//let mut words : Vec<String> = Vec::new();
-	//let infile : File = try!(File::open("/usr/share/dict/cracklib-small"));
-	let filename = "/usr/share/dict/cracklib-small";
-	let infile : File = File::open(filename).expect(
-		&format!("Error opening {}:", &filename)
-	);
-    let reader = BufReader::new(infile);
-	let tree = levtree::Tree::new(
-		reader.lines()
-			.map(|line| line.unwrap())
-			.collect());
-}

src/test.rs

@@ -1,6 +1,55 @@
 
 
-fn main(){
-	let mut ints = vec!(1,2,3,4,5,6);
-	ints[4] = 2;
+use std::collections::HashMap;
+
+// This struct has one lifetime parameter, 'src. The name is only used within the struct's definition.
+#[derive(Debug)]
+struct Config<'src> {
+    hostname: &'src str,
+    username: &'src str,
+}
+
+// This function also has a lifetime parameter, 'cfg. 'cfg is attached to the "config" parameter, which
+// establishes that the data in "config" lives at least as long as the 'cfg lifetime.
+// The returned struct also uses 'cfg for its lifetime, so it can live at most as long as 'cfg.
+fn parse_config<'cfg>(config: &'cfg str) -> Config<'cfg> {
+    let key_values: HashMap<_, _> = config
+        .lines()
+        .filter(|line| !line.starts_with('#'))
+        .filter_map(|line| line.split_once('='))
+        .map(|(key, value)| (key.trim(), value.trim()))
+        .collect();
+    Config {
+        hostname: key_values["hostname"],
+        username: key_values["username"],
+    }
+}
+
+// fn main() {
+//     let config = parse_config(
+//         r#"hostname = foobar
+// username=barfoo"#,
+//     );
+//     println!("Parsed config: {:#?}", config);
+// }
+
+
+struct Foo {}
+
+fn foo<T>(v : &[T]) {
+    for el in v.into_iter() {
+
+    }
+}
+
+// fn foo2(v : &mut Vec<Vec<isize>>) {
+//     let first = &v[0];
+//     let second = &mut v[1];
+
+//     second[0] = first[1] + second[2];
+// }
+fn main() { 
+    let s = String::from("🤑😂🤩🤬");
+    let c= s.chars().nth(1).unwrap(); 
+    println!("{}", c);
 }