Bert Freudenberg wrote:
Am 23.08.2006 um 21:15 schrieb cdrick:
Hi all -
not an important question here, more a discussion. I was wondering
which method is the more appropriate (nice and/or efficient) to
enumerate all the elements of a collection and the index of each
elements...
(a) ---- à la C
(1 to: collection size) do: [:index |
html render: 'Victime ', index printString.
html render:
collection at: index]
(b) --- indexOf
collection do: [:victim |
html render: 'Victime ', (collection indexOf:
victim) printString.
html render: victim]
(c) ---- keysAndValuesDo:
collection keysAndValuesDo: [:index :victim |
html render: index printString.
html render: member]
(d) ---- using a local var
| index |
index := 0.
collection do: [:victim | index := index + 1.
html render: 'Victime ', index printString.
html render: victim]
What solution would you suggest ?
I think we forget (a) and (d)
I like (c) but maybe (b) is more readable ?
Maybe there is another way ?
(c), though I like #withIndexDo: better since it mimics the #with:do:
pattern.
I would vote for #withIndexDo: too which has in 'intention revealing
name' :-)
And, please forget about (b), this is way too slow and wrong.
Slow because the complexity jump from O(n) to O(n²). Remember that
#indexOf: has to search for the element in all the collection.
Wrong because:
collection := #($a $b $a).
collection
do: [:each | Transcript
show: (collection indexOf: each);
space]
Will print '1 2 1' instead of '1 2 3'. Index answered by #indexOf: if
the first index on which the object is found.
Bye
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