[Pharo-project] could we agree to remove caseOf: and caseOf:otherwise:

Igor Stasenko siguctua at gmail.com
Sun Feb 13 01:52:58 CET 2011


On 13 February 2011 00:59, Levente Uzonyi <leves at elte.hu> wrote:
> On Sun, 13 Feb 2011, Igor Stasenko wrote:
>
>> Don't try to convince me that there are sort of problems which can be
>> solved only by using case statement :)
>
> We all know that it can be solved, but the solution won't be nicer at all,
> instead it will be a lot slower.
>
>> First, get rid of these integers in your code. Use symbolic names.
>> And then for dispatching using parameter, there is a #peform: primitive.
>
> The integers are from a binary stream, so I can't do much about it.
>
Oh yeah? Too bad for you then.

>>
>> So, then switch statement will be turned into:
>>
>> self peform: (self decode: someInteger)
>>
>> and this is how it should look like.
>> And again, if you can avoid using integers at all, use symbols , so
>> you don't have to decode/translate them.
>> Just do #perform.
>>
>> I thought that this is obvious for you.
>
> What you wrote here is obvious, but not an answer to my question. What
> should #decode: do? Use #detect:? Or a dictionary? Maybe a binary search on
> an array? Or should it be a bunch of #ifTrue:ifFalse: conditionals? (I guess
> the separate class per integer idea is abandoned, but who knows.)
>
I don't care. You should encapsulate them into something , which has a meaning.
Use bare numbers without any docs/comments/explanations to C.

> Also note that #perform:with: is ~11x slower on Cog than sending a message.
> And a send is a lot slower (~5.5x IIRC) than a direct assignment. That's
> ~55x combined slowdown not counting the integer->selector matching.
>
Slower comparing to someone who will read your code and try to
understand what it does.
THAT WILL BE SLOWER and that is most precious resource we have,  not
the CPU time.

Please read the
http://www.c2.com/cgi/wiki?PrematureOptimization
:)

>
> Levente
>
>>



-- 
Best regards,
Igor Stasenko AKA sig.




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