On Wed, Sep 3, 2014 at 8:37 AM, Camille Teruel <camille.teruel@gmail.com> wrote:

On 3 sept. 2014, at 17:26, Eliot Miranda <eliot.miranda@gmail.com> wrote:

On Wed, Sep 3, 2014 at 7:54 AM, Thierry Goubier <thierry.goubier@gmail.com> wrote:

2014-09-03 14:40 GMT+02:00 Marcus Denker <marcus.denker@inria.fr>:

with:do: on SequencableCollection checks that both collections have the same size (it raises an Error if not).

with: otherCollection do: twoArgBlock
�� "Evaluate twoArgBlock with corresponding elements from this collection and otherCollection."
�� otherCollection size = self size ifFalse: [self error: 'otherCollection must be the same size'].
�� 1 to: self size do:
�� [:index |
�� twoArgBlock value: (self at: index)
�� value: (otherCollection at: index)]

I think we should not do that:

1) it is slow

Are you sure about that one? The check is a constant cost disregarding the collection length, and, anyway, self size is reused just after that.

��
2) when the other is larger, is would work and just omit the rest��
3) if it is smaller, you will get an error anyway

I have a feeling I'm not in Pharo anymore, but in R instead ;)

+2. ��There are clear safety advantages in the check. ��If you want the "faster" protocol why not define withSomeOf:do: or some such?

Like Thierry I'm not sure that omitting the check brings a significant speedup.
However, not doing this check follows the robustness principle: "Be conservative in what you do, be liberal in what you accept from others".��

But it violates the "if it ain't broke don't fix it", "it means what it means", and "Smalltalk is a safe language" principles. ��That safety check finds bugs. ��If one wants a more relaxed contract, implement a new contract, don't break an existing contract that has stood for years.

��

I would even be more liberal with a:��

1 to: (self size min: otherCollection size) do: ....
:)

But you can write that if that's what you mean. ��But arbitrarily changing existing protocol for weak reasons when _it ain't broke_ is a recipe for chaos.

Thierry��

��

There are just three methods doing such a size check:

with:do:
with:collect:
reverseWith:do:
(the last one actually raises a�� SizeMismatch exception, it is the sole user of that exception)

Is there a reason why this makes sense?

I added an issue with a slice to clean it up:

https://pharo.fogbugz.com/f/cases/13946/speed-up-with-do-by-not-checking-size

�� Marcus

--
best,
Eliot

--
best,

Eliot