in midst of refactor

orchidlang/src/utils/string_from_charset.rs

@@ -0,0 +1,20 @@
+//! Generate valid names from numbers and a character set. For small numbers,
+//! the results should be substantially more memorable than the plain numbers.
+
+fn string_from_charset_rec(val: u64, digits: &str) -> String {
+  let radix = digits.len() as u64;
+  let mut prefix =
+    if val > radix { string_from_charset_rec(val / radix, digits) } else { String::new() };
+  let digit = digits
+    .chars()
+    .nth(val as usize - 1)
+    .unwrap_or_else(|| panic!("Overindexed digit set \"{}\" with {}", digits, val - 1));
+  prefix.push(digit);
+  prefix
+}
+
+/// Generate alphabetized names from numbers using a set of permitted
+/// characters. Especially practical in combination with De Bruijn indices
+pub fn string_from_charset(val: u64, digits: &str) -> String {
+  string_from_charset_rec(val + 1, digits)
+}