[ANSI-Smalltalk] Re: A list of interesting methods, ifNotNil:

[John O'Keefe]

VA Smalltalk also has some *Do: methods that do not imply iteration, but
they are few and relatively obscure (for the most part).  I don't like them,
but I am forced to live with them.  I am definitely against adding any more
selectors of their ilk -- either in our product or in the standard.

John O'Keefe [|], Principal Smalltalk Architect, Instantiations Inc.


On Mon, Sep 8, 2008 at 7:26 AM, Paolo Bonzini <bonzini at gnu.org> wrote:

>
> > I am now confused.
> > The actual code in Squeak is
> >
> >     ifNotEmptyDo: aBlock
> >         ^self isEmpty ifTrue: [aBlock value: self]
> >
> > It certainly doesn't involve any sending of the message #do:.
>
> Which is all but intention revealing.
>
> > x isEmpty ifTrue: [x do: monadicBlock]
> >
> > would, if x is a collection, never do anything at all with monadicBlock.
> > I take it that this should have been
> >
> > x isEmpty ifFalse: [x do: monadicBlock]
> >
> > and there is a name for that too:  #do:.
>
> Of course, but there is no existing name for #ifEmpty:ifNotEmptyDo:.
> Moreover, if you have another message #ifEmpty:ifNotEmpty: there is no
> hint that the two differ *in the arity of the second block*!
>
> If there were to be methods like #ifEmpty:, you should have only these
> four:
>
>   #ifEmpty:
>   #ifNotEmpty:
>   #ifEmpty:ifNotEmpty:
>   #ifNotEmpty:ifEmpty:
>
> plus possibly
>
>   #ifEmpty:ifNotEmptyDo:       (passing the second block to #do:)
>   #ifNotEmptyDo:ifEmpty:
>
> Furthermore, all parameters of all six methods should have variable
> arity, because unlike the nil/not-nil case, there are many empty
> collections and you may want to know it even in the empty case.  I agree
> that this is borderline -- I cannot think of a use case indeed, and most
> of the time you'll use #ifEmpty: just as a guard for ^self.
>
> > VisualWorks also has an if*Do: method or two.
> > GeneralBindingReference>>ifDefinedDo:
> > has nothing to do with #do:.
> > WindowManager>>activeControllerProcessIfBlockedDo:
> > also has nothing to do with #do:.
>
> But no #ifDefined: and #activeControllerProcessIfBlocked:.  I don't like
> those names very much, but that's nothing compared to overloading  "Do:"
> (which already has a well-known meaning in Smalltalk, i.e. "iterate") to
> mark arity.
>
> Paolo
>
>
>
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