[squeak-dev] #isNilOr:, #notNilAnd:

Eliot Miranda eliot.miranda at gmail.com
Sun Mar 22 21:48:51 UTC 2020

Hi Levente,

> On Mar 22, 2020, at 1:31 PM, Levente Uzonyi <leves at caesar.elte.hu> wrote:
> Hi Christoph,
>> On Sun, 22 Mar 2020, Thiede, Christoph wrote:
>> Hi all,
>> Levente:
>> > Both #isNilOr: and #notNilAnd: return a boolean value. It is possible to use these methods and ignore their return values. E.g.:
>> > 
>> > object ifNotNil: [ collection add: object ].
>> > 
>> > can be written as:
>> > 
>> > object isNilOr: [ collection add: object ].
>> > 
>> > or as:
>> > 
>> > object notNilAnd: [ collection add: object ].
>> I see your point. However, I think this would be a client problem rather than a design problem. :-)
> I fully agree this is a "client problem". Have a look at the senders of #in: in a Trunk image (82 senders).
> Most uses are entirely artifical (e.g. "I just avoid declaring a temporary for no reason"), some are outrageous (e.g. I don't want to use any temporaries, and I don't want to break the cascade chain I'm in, so I use various methods accepting blocks instead of separate statements just to write my code as a single expression"), very few are legitimate.

I have to say that I disagree that using ifNotNil: to avoid a temporary is outrageous :-). In fact it is part of Vassili’s design rationale for introducing ifNotNil: as an inlineable selector in the first place.  It not only localizes the declaration, changing yo to be a block argument, it makes it read-only ;a definition) and eliminates an assignment.  I’m very fond of using ifNotNil: to bind a value that is nil when it is to be ignored, and far from finding it outrageous, find it elegant.  Tastes differ.  Vice la difference.

> So, yes, we have a client problem. That is why I wrote what I wrote: I expect adding these would introduce more of those misuses as with #in:.
> Levente
>> The names tell you when you should send which message. Each selector has a different semantic that is also formed by its return value. If we neglected the return value, we could also critique the following:
>> aBoolean ifTrue: aBlock
>> can be written as:
>> aBoolean ==> aBlock
>> The return value is significant. Otherwise, you could compare the following:
>> aCollection do: aBlock
>> aCollection collect: aBlock
>> aCollection select: aBlock
>> ...
>> Eliot:
>> I have to apologize, you're absolutely right on ProtoObject vs. Object. Back in December, I did not yet understand the actual idea of ProtoObject. I absolutely agree with you that any extension of this kind should go to
>> Object instead.
>> Best,
>> Christoph
>> _________________________________________________________________________________________________________________________________________________________________________________________________________________________________
>> Von: Squeak-dev <squeak-dev-bounces at lists.squeakfoundation.org> im Auftrag von Stéphane Rollandin <lecteur at zogotounga.net>
>> Gesendet: Sonntag, 22. März 2020 09:03:42
>> An: squeak-dev at lists.squeakfoundation.org
>> Betreff: Re: [squeak-dev] #isNilOr:, #notNilAnd:  
>> > The whole point of ProtoObject is to support transparent proxies that
>> > raise doesNotUnderstand: when sent any message. All the protocol in
>> > ProtoObject other than doesNotUnderstand: is a colossal mistake and the
>> > result of serious misunderstanding of the utility and implementation of
>> > transparent forwarders.
>> +1
>> Stef

More information about the Squeak-dev mailing list