On Wed, 11 Sep 2019, Stéphane Rollandin wrote:

> Richard O'Keefe is making good points against the Squeak implementation 
> of method #collect:thenDo: in the Pharo-users list:

I disagree.

His idea is that #collect:thenDo: ought to work differently, calling 
Squeak's implementation "pointless", because it is what its name suggests: 
#collect: followed by #do:. But there's a small twist: the collected 
values are returned.

Then he brings up the red herring: examples where #collect: does something 
a naive user would not expect, and where #collect:as: should be used. Then 
blames it all on #collect:thenDo:.

Next, he shows how good those examples work in Pharo, with the new 
implementation. Even though he forgets to point out that the new
implementation has different semantics (when your blocks have side 
effects) and different return value (because it doesn't create an 
intermediate collection to return), which can break your code[1].

In the summary, he writes that "[the Squeak definition] does not improve 
readability. In fact, it REDUCES readability". I think having a fewer 
parentheses can help with legibility.
He also writes "[the Squeak definition] is useless with most collection 
classes.". I somewhat agree with this. I wouldn't use it in a method, but 
it sometimes comes handy in a workspace script (just like #in:).
Finally, "[the Squeak definition] does nothing to improve performance 
but just adds overhead.". I suppose no one wanted to improve performance 
with that method.

>
> https://lists.pharo.org/pipermail/pharo-users_lists.pharo.org/2019-September/044204.html
>
> I vote for the removal of this confusing method.

I'm not against deprecating it, because every now and then it brings up a 
similar discussion, but then all other methods of the same kind (*:then*:) 
must go as well from the collections.


Levente
[1] http://forum.world.st/Bad-reimplementation-of-Collection-gt-gt-collect-thenDo-in-Pharo-3-0-td4760774.html

>
> Stef
>
>