From: sto.mar@...
Date: 2012-08-04T22:41:30+09:00
Subject: Re: OptionParser error handling (InvalidArgument)

Am 04.08.2012 01:31, schrieb Panagiotis Atmatzidis:
> A bit off-topic now. In your next email you told me that you dislike
>  raising an exception in order to identify an integer. A second
> approach I found online was using regexp.

That's what I did in my version, too.

> However this was the answer I got from a user at 'stackoverflow'
> which convinced that this is the right way to go in ruby:
>
> "Sarah: you can use a Regex but in order to handle all the cases that
> Ruby does when parsing integers (negative numbers, hex, octal,
> underscores e.g. 1_000_000) it would be a very big Regex and easy to
>  get wrong. Integer() is canonical because with Integer ()you know
> for sure that anything that Ruby considers an integer literal will be
> accepted, and everything else will be rejected. Duplicating what the
> language already gives you is arguably a worse code smell than using
> exceptions for control. – Avdi " from
> http://stackoverflow.com/questions/1235863/test-if-a-string-is-basically-an-integer-in-quotes-using-ruby

Imo there is no "canonical" way that fits all use cases.

Here, in connection with command line arguments, I prefer
using a regexp (probably as a second choice after using the Integer
cast from optparse): I do not expect an octal integer as user input,
the regexp is rather simple, and the approach is flexible.
I can for example test for integers or for nonnegative integers, with

/\A[+-]?\d+\Z/ === str  or  /\A[+]?\d+\Z/ === str

Partly a matter of taste.


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