From: Joe Van Dyk <joevandyk@...>
Date: 2005-12-23T07:25:52+09:00
Subject: Re: String > Integer Conversion Problem

On 12/22/05, Matthew Feadler <matthew@feadler.com> wrote:
> First, thanks all very much for the lively discussion thus far.  It's
> proven very useful.
>
> Timothy Hunter wrote:
> > The Integer() method raises ArgumentError if given an empty,
> > non-numeric, or otherwise non-well-formed string.
>
> Hmm...apparently not--at least not w/ 1.8.2 on mswin32.
>
> This:
>
>  begin
>    one, two = ARGV.map{ |n| Integer(n) }
>  rescue ArgumentError
>    puts "Usage..."
>    exit
>  end
>
>  puts one
>  puts two
>
> Outputs:
>
>  nil
>  nil
>
> When fed no command-line arguments.  It does work as intended if any of
> the args are non-empty strings, however.
>
> Also:
>
>  raise "Hey, '#{ arg }' needs to be a number" if !arg.match(/^\d*$/)
>
> I'm a regexp neophyte, without skill or clue.  Any suggestions on
> tutorials?

Dunno about tutorials, but:

the / characters indidicate that whatever is between them is a regular
expression.
^ is the beginning of a line (or string)
\d is a digit (i.e. 0 1 2 3 4 5 6 7 8 or 9)
* means to match 0 or more of the previous thing.
$ is the end of the line.

So, /^\d*$/ means that the entire string from beginning to end is
comprised of zero or more digits.  So, a minus sign ('-') or any
non-digit somewhere in the string would fail the check.