Re: [boost] Interest in breakable labeled scope emulation?

Subject: Re: [boost] Interest in breakable labeled scope emulation?
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-01-13 17:32:04

Le 13/01/13 20:37, Brian Ravnsgaard Riis a écrit :
> Den Sun, 13 Jan 2013 20:30:14 +0100 skrev Vicente J. Botet Escriba 
> <vicente.botet_at_[hidden]>:
>
> [snip]
>> Of course in order to be really structured the jumping to the 
>> underlying label should be forbiden (by the compiler), but I don't 
>> think that a preprocessor solution could take care of this. So the 
>> following not desired and not structured code could compile even if 
>> we would like an compile error.
>>
>>
>> BOOST_NAMED_BLOCK(L)
>> {
>> // ...
>> }
>> // [1]
>> //...
>> BOOST_BREAK(L); // go to [1]
>
> So, the underlying idea is to get something like "break" and 
> "continue" to work inside any "named" block, not just loops? If so (as 
> you demonstrate above) I'm fairly certain a correct solution cannot be 
> implemented using just the preprocessor.
I believe preprocesor can provide a solution that allows you write 
correct programs but don't avoid bad uses. Even in this case, exiting 
from nested loops could be more easy to write/read as showed here.

BOOST_NAMED_BLOCK(L)
for(;;)
{
   while (cnd)
   {

     if (cnd2) BOOST_BREAK(L); // go to [1]
   }
}
// [1]

Well this is always subjective ;-)

Best,
Vicente