From: Robert Klemme <shortcutter@...>
Date: 2010-11-03T21:31:20+09:00
Subject: Re: Regular Expression

2010/11/3 Jesús Gabriel y Galán <jgabrielygalan@gmail.com>:
> On Wed, Nov 3, 2010 at 11:10 AM, Robert Klemme
> <shortcutter@googlemail.com> wrote:
>> Interesting approach.  I would simply have done
>>
>> def check(input)
>>  raise ArgumentError, "Illegal chars in sequence: %p" % input unless
>> /\A[A-D]{0,4}\z/ =~ input
>>  cnt = Hash.new 0
>>  input.scan /./ do |m|
>>    raise ArgumentError, "Illegal sequence %p" % input if (cnt[m] += 1) > 1
>>    # alt: return false
>>  end
>>  # alt: true
>> end
>
> There are different requirements for each letter. Adapting your solution:

Good point!  I overlooked that.

> def check(input)
>  limits = {'A' => 1, 'B' => 1, 'C' => 1, 'D' => 2}
>  raise ArgumentError, "Illegal chars in sequence: %p" % input unless
> /\A[A-D]{0,4}\z/ =~ input
>  cnt = Hash.new 0
>  input.scan /./ do |m|
>    cnt[m] += 1
>  end
>
>  cnt.each do |letter, amount|
>    raise ArgumentError, "Illegal chars in sequence: %p" % input if
> amount > limits[letter]
>  end
> end

I'd rather do:

def check(input)
 raise ArgumentError, "Illegal chars in sequence: %p" % input unless
/\A[A-D]{0,4}\z/ =~ input
 cnt = {'A' => 1, 'B' => 1, 'C' => 1, 'D' => 2}
 input.scan /./ do |m|
   raise ArgumentError, "Illegal sequence %p" % input if (cnt[m] -= 1) < 0
   # alt: return false
 end
 # alt: true
end

:-)

Cheers

robert

-- 
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