Parse "#REPLACE" macro in MML.

src/mfvi.rs

@@ -0,0 +1,28 @@
+struct Translation<'a> {
+    find: &'a str,
+    replacement: &'a str,
+}
+
+pub fn replace_chars(input: &str) -> String {
+    let trs: Vec<Translation<'_>> = input
+        .lines()
+        .filter_map(|line| {
+            line.strip_prefix("#REPLACE ")
+                .and_then(|l| l.rsplit_once(' '))
+                .and_then(|(first, second)| {
+                    let length = std::cmp::min(first.len(), second.len());
+                    Some(Translation {
+                        find: &first[0..length],
+                        replacement: &second[0..length],
+                    })
+                })
+        })
+        .collect();
+
+    let mut new = input.to_string();
+    for tr in trs {
+        new = new.replace(tr.find, tr.replacement);
+    }
+
+    new
+}