From: Patrick Deuster <pdeuster@...>
Date: 2006-02-05T22:27:12+09:00
Subject: Re: Quiz #65, Principle of Great Surprise, and Array.delete sledgehammer

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William James wrote:
> Dave Howell wrote:
>   
>> I thought I was actually going to enter my first RubyQuiz, but I've
>> spent three times as much time trying to get Ruby to stop surprising me
>> as I have trying to implement my algorithm, and I've had to abandon my
>> effort since I don't have the time to spend. Sigh.
>>
>> Can somebody explain to me how I'm supposed to delete a *single*
>> element from an array based on equivalence with an object? and get back
>> said array with said element deleted?
>>
>> In other words....
>>
>> ar = [1, 2, 3, 8, 15, 15, 8]
>>
>> ar.delete_one_element!(15)
>> => [1, 2, 3, 8, 15, 8]
>>
>> ar.delete_one_element!(14)
>> => [1, 2, 3, 8, 15, 15, 8]
>>
>> ar.delete_one_element!(nil)
>> => [1, 2, 3, 8, 15, 15, 8]
>>
>> I did find so many different ways of not doing this....
>>
>> Too enthusiastic....
>> ar.delete(15)
>> => 15
>> ar
>> => [1, 2, 3, 8, 8]
>>
>> Right results, wrong output...
>> ar.slice!(ar.index(15))
>> => 15
>> ar
>> => [1, 2, 3, 8, 15, 8]
>>
>> and also surprised me by not handling 'nil' as I wanted...
>> ar.slice!(ar.index(13))
>> TypeError: no implicit conversion from nil to integer
>>          from (irb):8:in `slice!'
>>          from (irb):8
>>
>>
>> I mean, this seems so, er, obvious! "Please find one instance of this
>> object in the array, and return to me the array without that object. If
>> the array doesn't have that object, then just give the array back to
>> me."
>>     
>
> This may not be of any use to you, but here's a way to delete all
> elements but the first:
>
> class Array
>   def no_dup!( x )
>     (i = index(x)) && delete( x ) && insert(i,x)
>     self
>   end
> end
>
> And here's another version of delete_one_element!.
>
> class Array
>   def delete_one_element!( x )
>     (i = index(x)) && delete_at( i )
>     self
>   end
> end
>
>
>
>   
And here's yet another version, similar to the ones already posted though:

class Array
  def delete_one! n
    (i = index(n)) ? delete_at(i) : nil
  end
end

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