Add function to calculate lenvenshtein distance of two strings

Will be useful to make import or usage suggestions.

crates/aiken-lang/src/levenshtein.rs

@@ -0,0 +1,42 @@
+use std::cmp;
+
+/// Calculate Levenshtein distance for two UTF-8 encoded strings.
+///
+/// Returns a minimum number of edits to transform from source to target string.
+///
+/// Levenshtein distance accepts three edit operations: insertion, deletion,
+/// and substitution.
+///
+/// References:
+///
+/// - [Levenshtein distance in Cargo][1]
+/// - [Ilia Schelokov: Optimizing loop heavy Rust code][2]
+///
+/// [1]: https://github.com/rust-lang/cargo/blob/7d7fe6797ad07f313706380d251796702272b150/src/cargo/util/lev_distance.rs
+/// [2]: https://thaumant.me/optimizing-loop-heavy-rust/
+pub fn distance(source: &str, target: &str) -> usize {
+    if source.is_empty() {
+        return target.len();
+    }
+    if target.is_empty() {
+        return source.len();
+    }
+
+    let mut distances = (0..=target.chars().count()).collect::<Vec<_>>();
+
+    for (i, ch1) in source.chars().enumerate() {
+        let mut sub = i;
+        distances[0] = sub + 1;
+        for (j, ch2) in target.chars().enumerate() {
+            let dist = cmp::min(
+                cmp::min(distances[j], distances[j + 1]) + 1,
+                sub + (ch1 != ch2) as usize,
+            );
+
+            sub = distances[j + 1];
+            distances[j + 1] = dist;
+        }
+    }
+
+    *distances.last().unwrap()
+}

crates/aiken-lang/src/lib.rs

@@ -9,6 +9,7 @@ pub mod builder;
 pub mod builtins;
 pub mod expr;
 pub mod format;
+pub mod levenshtein;
 pub mod parser;
 pub mod pretty;
 pub mod tipo;