From: sto.mar@...
Date: 2013-07-31T05:35:58+09:00
Subject: Re: How to check an input IS an integer ?

Am 30.07.2013 20:51, schrieb Captain Ishido:
> Le 30/07/2013 12:55, sto.mar@web.de a 辿crit :
>> Am 30.07.2013 12:03, schrieb Captain Ishido:
>>> Hi everyone !
>>> I have a little problem since a few days. I would like to check that my
>>> user (I am writing a small program) had type an integer while I asked him.
>>
>> There are several possibilities, the one I like best in this case
>> is using a Regex (Note that user input is always a String):
>>
>> 2.0.0p247 :005 > answer = '123'
>>  => "123"
>> 2.0.0p247 :006 > /\A[0-9]+\z/ === answer
>>  => true
>> 2.0.0p247 :007 > answer = '123abc'
>>  => "123abc"
>> 2.0.0p247 :008 > /\A[0-9]+\z/ === answer
>>  => false
>>
>> Other possibilities can easily be found by searching the archives,
>> e.g. using Integer(), (which involves rescuing exceptions, which I
>> do not like for this use case too much).
>>
>> Regards,
>> Marcus
>>
>>
> I've found a 'solution'. I don't like it but *cough* it works.
> If you're a REAL programmer, don't read.
> -----------------------------------------------
> # Let's do DIRTY things
> # (Don't try do to this at home, kids !)
> answer=""
> answer=answer.to_i
> while answer == 0 do
> 	puts "Please type an integer : "
> 	answer = readline.chomp
> 	answer=answer.to_i
> end

Depending on the use case, `0' might be a valid answer...


Something like this should work:

  answer = nil
  until /\A[0-9]+\z/ === answer
    print 'Enter an integer: '
    answer = gets.chomp
  end

  number = answer.to_i
  puts "Your answer: #{number}"


Regards,
Marcus


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