2011/10/18 Eliot Miranda <eliot.miranda at gmail.com>:
>
>
> On Tue, Oct 18, 2011 at 1:58 AM, Bert Freudenberg <bert at freudenbergs.de>
> wrote:
>>
>> On 18.10.2011, at 05:11, Chris Muller wrote:
>>
>> > (From vm-dev list)
>> >> But I much prefer foo ~~ bar ifTrue: than foo == bar ifFalse:.
>> >
>> > Hi Eliot.  May I ask why you prefer the former over the latter?
>> >
>> > I'm interested because I'm working on an application where the folks
>> > involved prefer something similar, to where they write (expr) not
>> > ifTrue: [ ] rather than (expr) ifFalse: [ ].
>> >
>> > I know you wouldn't do that but your statement definitely piqued my
>> > surprise and curiosity.
>>
>> Maybe this is a clue: very few other programming languages have an
>> "else"-case without a preceding "if true". So maybe for people versed in
>> multiple languages the ifFalse: feels wrong?
>
> For me, it's not about feeling right or wrong, it's about directly
> expressing intent. For example, in some loop where a predicate is being used
> to select or reject elements I would write "obj predicate ifTrue:" if I were
> looking for the element based on predicate and "obj predicate ifFalse:" if I
> were trying to filter-out elements based on predicate, just as I'd write
> collection select: [:e| e predicate] to select items based on predicate
> and collection reject: [:e| e predicate] to filter them out, and I would
> /not/ write collection select: [:e| e predicate not] to filter them out
> unless performance was really really important (since reject: adds another
> block activation for each element).  I'm trying to communicate whether I'm
> selecting or rejecting based on predicate, and not wanting the reader to go
> through mental hoops by internally collapsing predicate not ifFalse: to
> predicate ifTrue: and vice verse.
>>
>> I personally like "expr ifFalse:" better than "expr not ifTrue:".
>
> Agreed.  expr not ifTrue: & expr not ifFalse are perverse.
>

He He, Eliot, I saw your initials stamped on this quite defensive code:

	(self selectedClass notNil
	 and: [multiWindowState notNil
	 "Can only support multi-window if original window has all the right panes."
	 and: [multiWindowState prototype isHierarchy not]]) ifTrue:

Probably a negative day ;) (no offense, I'd like to hide all my own
production away)
However, I'm not sure whether (or not) the negated form makes the
intention clearer...

	(self selectedClass isNil
	 or: [multiWindowState isNil
	 "Can only support multi-window if original window has all the right panes."
	 or: [multiWindowState prototype isHierarchy]]) ifFalse:

Nicolas

>>
>> And I read "~~" as "not identical" which also has a mental "not" in it, so
>> I prefer "== ifFalse" :)
>
> Ah, there we differ.  I view == and ~~ as complementary predicates.  If I'm
> writing foo == bar ifTrue: I'm clearly selecting, and foo ~~ bar ifTrue: I'm
> clearly rejecting, but foo == bar ifFalse: is IMO worse (more cognitively
> demanding) than foo ~~ bar ifTrue:.
>
>
>>
>> - Bert -
>>
>>
>>
>
>
>
> --
> best,
> Eliot
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>