[ANSI-Smalltalk] Behaviour of #collect:

[Peter van Rooijen]

On Tue, 23 Sep 2008 05:40:12 +0200, Richard A. O'Keefe <ok at cs.otago.ac.nz>  
wrote:

>
> On 23 Sep 2008, at 4:40 am, Eliot Miranda wrote:
>
>> what about
>>      Collection class collect: aBlock from: aCollection
>> e.g.
>>      Array collect: [:each | each codePoint] from: 'abc'
>> ?
>>
> Because there isn't any #collect:from: in the Smalltalks
> I use.

I think that Eliot was simply proposing another name, that speaks better  
to him. So whether or not this name appears anywhere else might not be of  
overriding importance. #collect:from: appeals more to me, too. I think I'd  
remember that easily, when I run into a myCollection collect: ... that I  
realize (or find out) won't work as I want.

I think you have identified 2 separate and valid issues:

1) Would adding #withAll:collect: to every class that has #withAll:
be considered a good move?

Are you talking about a general method on Collection class that would be  
essentially this?

Collection class>>#collect: monadicBlock from: collection
| elements |
elements := OrderedCollection new
.
collection do: [:x | elements add: (monadicBlock value: x)]
.
^self withAll: elements

(warning: untested code, so contains bugs)

Where applicable, subclasses of Collection would then contain optimized  
(specifically, avoiding the creation of the intermediate elements  
collection), but otherwise equivalent implementations.

Did I understand you correctly?

2) What exactly should #collect: do when sent to an object that
belongs to a class whose instances cannot hold the results that
the block returns?

This seems like a hard one, practically. Whatever current implementations  
do, would be hard to change. If we want a standard that is accepted, we  
probably shouldn't try to go that way. But isn't the upside that the  
problem becomes kinda moot with the addition of the class method discussed  
above?

> I've already mentioned the operation I added,
> which is named consistently with the ANSI methods, namely
> 	<class> withAll: collection collect: aBlock
> This also goes with
> 	<collection> addAll: collection collect: aBlock
>
> #withAll:collect: is nice, and I'd like to see it in the
> new standard, but it's long winded and it's limiting.

I think your idea is valid (and I don't see why it would be long winded  
and limiting). I like Eliot's proposed name better. Does someone see a  
problem with this? If not, I'd like to propose to add this to the new  
standard.

Cheers, Peter

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-- 
Peter van Rooijen
Esstede 19
1112 EP Diemen
m: 06-2854 2048