core :: Char :: is_letter
assert 'A'.is_letter == true assert 'A'.is_letter == true assert 'z'.is_letter == true assert '$'.is_letter == false
# Is self a letter? (from 'A' to 'Z' and 'a' to 'z') # # assert 'A'.is_letter == true # assert 'A'.is_letter == true # assert 'z'.is_letter == true # assert '$'.is_letter == false fun is_letter : Bool do return is_lower or is_upper end