Ruby: How to find out if a character is a letter or a digit?

Question

I just started tinkering with Ruby earlier this week and I\'ve run into something that I don\'t quite know how to code. I\'m converting a scanner that was written in Java into R

Answer 1

Regular expression is an overkill here, it's much more expensive in terms of performance. If you just need a check is character a digit or not there is a simpler way:

def is_digit?(s)
  code = s.ord
  # 48 is ASCII code of 0
  # 57 is ASCII code of 9
  48 <= code && code <= 57
end

is_digit?("2")
=> true

is_digit?("0")
=> true

is_digit?("9")
=> true

is_digit?("/")
=> false

is_digit?("d")
=> false