Smaller char replacing
Copied it from the rust doc: https://doc.rust-lang.org/std/str/pattern/trait.Pattern.html#impl-Pattern%3C%27a%3E-3
Edited by Lorenzo Miglietta
Copied it from the rust doc: https://doc.rust-lang.org/std/str/pattern/trait.Pattern.html#impl-Pattern%3C%27a%3E-3