The idea in Smalltalk is to push a method as high as makes sense

and no higher, so that if you send a message to an object where it

really does not make sense (like trying to add two strings) you

get a runtime failure.�� (Try asking an old-timer about automatic

conversions in PL/I some time.)�� Now Lisp *did* define NIL=false,

anything else=true, and Lisp came before Smalltalk, and you can

bet the designers of Smalltalk knew about this possibility.

As a particular example, I seem to forget to initialise variables

embarrassingly often, and having x ifTrue: ... ifFalse: ... fail

noisily because x was still nil has made my life simpler too often.

On 20 March 2018 at 02:16, Petr Fischer <petr.fischer@me.com> wrote:

That sounds correct. In this context, my "universal ifTrue:" is really terrible idea.

Thanks for clarification! pf

> Why would you do such aberration?
>
> It goes against the "fail noisily" "Rule of Repair": Developers should
> design programs that fail in a manner that is easy to localize and
> diagnose or in other words ��fail noisily��. This rule aims to prevent
> incorrect output from a program from becoming an input and corrupting
> the output of other code undetected.
>
> It is semantically incorrect, if needed, I don't see why, you sould
> implement it in�� your own class. But when I needed to do such "if"
> handlers, I did it using meaningful selectors like #ifGranted: or
> #ifSucceeded:, or the well known #ifEmpty:
>
> Regards,
>
> Esteban A. Maringolo
>
>
> 2018-03-19 9:40 GMT-03:00 Petr Fischer <petr.fischer@me.com>:
> >> Infinite recursion ?
> >>
> >> You use #ifTrue: in your implementation of Object>>#ifTrue:
> >>
> >> Plus, non-booleans cannot meaningfully respond.
> >>
> >> How would you define the semantics of
> >>
> >> 123 ifTrue: [ ... ]
> >
> > 123 is not "true", so, ignore the block.
> > Do the ifTrue block only if the receiver is instance of True (true). Everything else is not "true" :)
> >
> > I missed the recursion, yes, but it could be done another way.
> >
> >>
> >> > On 19 Mar 2018, at 10:18, Petr Fischer <petr.fischer@me.com> wrote:
> >> >
> >> > Hello, I have some sort of philosophical question about ifTrue:/ifFalse: implementation.
> >> >
> >> > Now, ifTrue: is defined in the Boolean class (subclassResponsibility) + in True and False classes, so, we can send this message to the boolean expressions (instances) only, otherwise DND occurs.
> >> >
> >> > But we can also define one universal ifTrue: right in the Object class, in this style:
> >> >
> >> > Object>>ifTrue: ....
> >> >�� (self = true) ifTrue: [ ... ].
> >> >
> >> > then, we can send ifTrue: message to ANY object and it will work correctly without DND exception on non-boolean objects.
> >> >
> >> > Is something bad about this idea?
> >> >
> >> > Thanks! pf
> >> >
> >>
> >>
> >
>