Adding two characters isn't strictly needed for that -- you're relying on the assumption that (c - 'a') is of type character, but it's actually the offset betwe

Adding two characters isn't strictly needed for that -- you're relying on the assumption that (c - 'a') is of type character, but it's actually the offset between two characters. The rules for those two types would be: char + char = invalid char + offset = offset + char = char offset + offset = offset char - char = offset char - offset = char offset - char = invalid offset - offset = offset Given that, (c - 'a') + 'A' is perfectly valid without adding two characters. edit: formatting