From: 7stud -- <bbxx789_05ss@...>
Date: 2007-10-26T02:52:18+09:00
Subject: Re: Change a string to an integer, report an error if the string does not represent an integer?

Randy Kramer wrote:
> Can anybody point me to a way to check if a string represents a valid 
> integer
> and then convert it to an integer?
> 
> It is very likely the string will contain leading zeros, and should not
> contain any trailing non-numeric characters.
> 
> Per the documentation (pickaxe 2), to_i won't quite do it, it will just 
> ignore
> trailing non-numeric characters.
> 
> Thanks!
> 
> Randy Kramer



>Integers can also be negative. 

Integers can also have leading '+' signs.  :)

Another way:


def valid_int?(str)
  start = true

  str.each_byte do |char|
    if start
      start = false
      if char == ?+ or char == ?-
        next
      end
    end

    if char < ?0 or char > ?9
      return false
    end
  end

  return true
end

strings = ['0013abc', '0025', '-0030', '+051', '00-1', '-abc72']
strings.each do |str|
  if valid_int?(str)
    puts str.to_i
  else
    puts 'invalid int'
  end
end
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