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Date: Sun, 24 Apr 2011 12:54:32 -0700
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: Is it sign of bad Object Oriented programming?
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On 4/24/2011 12:21 PM, Lew wrote:
> Eric Sosman wrote:
>
>> Merciadri Luca wrote:
>>> Let us consider a class Class and an object myObj of type Class. Let
>>> there be a method myMeth defined in the Class class.
>>>
>>> Are there some cases where typing e.g.
>>> ==
>>> myObj.myMeth(myObj)
>>> ==
>>> is not considered as `bad style?' That is, are there, more generally,
>>> some situations where passing an instanciated object to a method of
>>> this object is a good way of achieving something?
>
>> boolean arrayHasEqualThing(Thing[] array, Thing thing) {
>> for (Thing t : array) {
>> if (t.equals(thing)) // Look here!
>> return true;
>> }
>> return false;
>> }
>
> This differs from the problem statement, which has the argument
> reference the same instance as that through which the (instance) method
> is called. The method that you show here is a candidate for 'static'
> scope as it does not depend on the state of 'this'. In particular, there
> is no guarantee in this proposal that 't' or 'thing' point to the 'this'
> instance, nor to the same instance as each other.
>

Consider an arithmetic type Widget, like BigInteger, with a multiply
method that returns the Widget representing the product of this and a
Widget argument.

Now write Widget's square method:

public Widget square() {
   return multiply(this);
}

Is that what is being discussed?

Patricia