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

Use a regular expression that matches letters & digits:

def letter?(lookAhead)
  lookAhead.match?(/[[:alpha:]]/)
end

def numeric?(lookAhead)
  lookAhead.match?(/[[:digit:]]/)
end

These are called POSIX bracket expressions, and the advantage of them is that unicode characters under the given category will match. For example:

'ñ'.match?(/[A-Za-z]/)     #=> false
'ñ'.match?(/\w/)           #=> false
'ñ'.match?(/[[:alpha:]]/)  #=> true

You can read more in Ruby’s docs for regular expressions.