Paolo
why Iterable as a superclass of stream and collection?
Why not a trait?
Then I'm wondering why this would be faster.
Hi all, I would like to ask your opinion about adding the "Iterable"
common
superclass of Collection and Stream to Pharo. This is already in GNU
Smalltalk and is in my opinion a better alternative to the "lazy
collections" idea.
Here is how I did it:
1) Well, create the class and make Stream/Collection subclasses of it.
2) Push there from Collection #do: (abstract), #inject:into:, #fold: (if
you have it), #do:separatedBy:, #detect:, #detect:ifNone:, #count: (if
you
have it), #allSatisfy:, #noneSatisfy:, #conform:, #contains: (if you
have
the last two).
3) Add #nextPutAllOn:
nextPutAllOn: aStream
"Write all the objects in the receiver to aStream"
self do: [ :each | aStream nextPut: each ]
4) Change Stream>>#nextPutAllOn: to use "source nextPutAllOn: self".
5) On top of this I added "filtering" streams to implement #select:,
#reject: and #collect:. Here is a clean-room MIT implementation:
Stream >> select: block
^FilterStream new stream: source block: block result: true
Stream >> reject: block
^FilterStream new stream: source block: block result: false
Stream >> collect: block
^FilterStream new stream: source block: block
FilterStream >> atEnd
atEnd isNil ifTrue: [
[stream atEnd ifTrue: [^atEnd := true].
next := stream next.
(block value: next) == result] whileFalse.
atEnd := false].
^atEnd
FilterStream >> next
self atEnd ifTrue: [^pastEnd].
atEnd := nil.
^next
CollectStream >> atEnd
^stream atEnd
CollectStream >> next
^block value: stream next
On Jul 16, 2009, at 9:57 AM, Paolo Bonzini wrote:
>
>> If people really want to be able to combine enumerator methods for
>> higher efficiently the Collection hierarchy should be fixed. Having
>> external iterator objects like in C++ and Java is not that bad after
>> all:
>>
>> result := aCollection iterator
>> select: [ :e | ... ];
>> collect: [ :e | ... ];
>> contents
>
> It's already there and it's called #readStream. :-) It only lacks
> #size.
>
> See http://code.google.com/p/pharo/issues/detail?id=958 for an outline
> of the implementation.
>
> Paolo
>
>
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