In ruby how do you tell if a string input is in uppercase or lowercase?

Question

I am trying to write a program that when a single letter is inputted, if it\'s in uppercase, leave it in uppercase and return it, and if it\'s in lowercase, then convert to

Answer 1

Just convert the string to upper case and compare it with the original

string == string.upcase

or for lowercase

string == string.downcase

 

Edit: as mentioned in the comments the solution above works with English letters only. If you need an international solution instead use

def upcase?(string)
    !string[/[[:lower:]]/]
end

which uses a regular expressions to scan the string for lowercase letters and the negates the finding to tell whether the string is all uppercase.