[chuck-dev] for loop, empty conditional statement, possible fix

[Szilveszter Tóth]

Hi Ge!

Thanks for the fix, it works!

Regards,
Szilveszter (aka Hillaby)

Ge Wang escribió:
> Hi Szilveszter and Kassen!
>
> Thanks for the discussion, and thanks to Szilveszter for the report 
> and the fix (it's right on)!  I've included the fix into the source, 
> with a minor tweak - I think for now, we are going to disallow empty 
> for conditions, and will require an explicit true.  For example:
>
> for( ; ; )
> { /*...*/ }
>
> now gets the follow compiler error:
>
> [foo.ck]:line(1): empty for loop condition...
> [foo.ck]:line(1): ...(note: explicitly use 'true' if it's the intent)
> [foo.ck]:line(1): ...(e.g., 'for( ; true; ){ /*...*/ }')
>
> This will still leave the possibility of for( ; ; ) to work in the 
> future, but it seems harder going the other way...
>
> I hope this helps and thanks again for the fix!
>
> All the best,
> Ge!
>
> ~~~
> Ge Wang
> Assistant Professor
> Center for Computer Research in Music and Acoustics (CCRMA)
> Stanford University
> http://ccrma.stanford.edu/~ge/
> ~
> Co-founder, CTO, Chief Creative Officer
> Smule
> http://www.smule.com/ | http://twitter.com/gewang
> ~~~
>
> On Fri, 23 Oct 2009, Kassen wrote:
>
>> Szilveszter
>>
>>
>>       I would not go scientific here... :) I just wrote down a line of
>>       code which I expected to work... However, I've  never written
>>       down anything like:
>>
>>       if() {} or while() {}
>>
>> Erm, no. :-)
>>  
>>       which I suspect would give a C compiler error.
>>
>> I should hope so, yes. If I were a parser I'd go on strike over that.
>>  
>>       My point is that the first and the third part of the for()
>>       statement can be omitted as for now (in ChucK). So I don't see a
>>       point why the second one shouldn't work the same way.
>>
>>
>> The one perspective I could see is that the first and third are 
>> actions, and
>> omiting those seems quite natural if we need no action to be taken. The
>> second is a condition and it's less intuitively clear what omiting it 
>> should
>> mean. Borrowing from C seems quite natural.
>>
>> I seem to remember there were previous issues with more exotic "for" 
>> loops
>> in ChucK, btw. Previously there was a issue with stuffing more than one
>> thing (some of which could be commands that need not evaluate to true or
>> false, as long as the last one did), that would also crash. My memory is
>> hazy on this as I didn't see the use but now I do, it's probably to get
>> those out of the scope of any "continue" commands we might use.
>>
>> Most important to me is that I don't think that anything that comes 
>> through
>> the parser should crash the whole VM. To be perfectly clear; I don't
>> disagree with anything here, I'm just trying to see whether this is or
>> should be part of a larger structure that I should understand. I know 
>> I can
>> sometimes come across like I'm arguing when doing that. I think that 
>> urge is
>> satisfied for now :-).
>>
>> Thanks again,
>> Kas.
>>
>>
>>
>>
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