On Thu, 11 Mar 2010, Henrik Johansen wrote:
Den 11.03.2010 01:54, skrev Nicolas Cellier:
2010/3/11 Igor Stasenko <siguc...@gmail.com>:
On 10 March 2010 15:07, Nicolas Cellier
<nicolas.cellier.aka.n...@gmail.com> wrote:
self collect: aBlock as: Set
One more time, i found this very beatiful and useful extension to
Collection protocol.
And i am proud being a witness when this thing is born! :)
Yes,
I remember saying I was not convinced some times ago...
http://lists.squeakfoundation.org/pipermail/squeak-dev/2008-June/129457.html
Being able to change own opinion is a good thing !
Nicolas
I have to admit, I still don't quite see what's wrong with
1.
(self collect: aBlock) asSet
('foo' collect: [ :each | each asciiValue ]) asSet "===> boom :)"
or
2.
mySet := Set new: self size.
self do: aBlockAddingToMySetAtEnd.
That's ok, but it's two lines + a temporary declaration.
or (well, this one is IMO indeed a bit ugly)
3.
self inject: (Set new:self size) into:
[ :sub :next |
sub add: next collectValue; yourself ] ...
Sure, they're a bit verbose, and when you'd like to use 1 vs 2 or 3
varies abit on the collection contents, but they all work in all
dialects, and aren't THAT much longer, unless your collect block is
really short.
I did a quick sampling (not representative) and found that 1 out of 20
collect blocks is longer than a single line.
#collect:as: is a solution to the problem about #species which limits the
use of #collect: in some cases. You can find the proposal about
#collect:as: here if you're interested:
http://lists.squeakfoundation.org/pipermail/squeak-dev/2009-November/141245.html
And who knows, maybe other dialects will implement these methods too,
until then, don't use #collect:as: in code which should be portable across
dialects.
Levente
Cheers,
Henry
2010/3/10 Mariano Martinez Peck <marianop...@gmail.com>:
Hi. I was needing something like the SQL select distinct, that doesn't take
into account repeated objects. I didn't found anything useful in Collection,
and thus, I have implemented this:
Collection >> collectDistinct: aBlock
collectDistinct: aBlock
"Evaluate aBlock with each of the receiver's elements as the argument.
Collect the resulting values into a Set, thus repeated objects will not
be present.
Answer the new collection."
| newSet |
newSet := self species new asSet.
self do: [:each | newSet add: (aBlock value: each)].
^ newSet
Is there a better way ? Do you think it make sense to put this in Pharo ?
Cheers
Mariano
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--
Best regards,
Igor Stasenko AKA sig.
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