Ruby determining whether a letter is uppercase or not

Question

The question is very simple and probably have thousand of answers, but i am looking for some magical ruby function.

Problem: To determine whether a letter is upcase or not i.e belongs to A-Z.

Possible Solution:

array = ["A","B", ....., "Z"]
letter = "A"
is_upcase = array.include? letter

Please note that "1" is not an uppercase letter.

Is there any magical ruby function which solve the problem with less code?

Answer 1

You can use POSIX character classes:

• /[[:lower:]]/ - Lowercase alphabetical character
• /[[:upper:]]/ - Uppercase alphabetical

Example:

def which_case(letter)
  case letter
  when /[[:upper:]]/
    :uppercase
  when /[[:lower:]]/
    :lowercase
  else
    :other
  end
end

which_case('a') #=> :lowercase
which_case('ä') #=> :lowercase
which_case('A') #=> :uppercase
which_case('Ä') #=> :uppercase
which_case('1') #=> :other

Or with a simple if statement:

puts 'lowercase' if /[[:lower:]]/ =~ 'a'
#=> lowercase