Anoying problem, but what else can be done?

[Don Clugston]

Frits van Bommel wrote:
> BCS wrote:
>> this fails
>>
>> foreach(i, j; Tuple!(1,2,3,4)
>> {
>>  loopLable: while(test())
>>  {
>>    while(otherTest())
>>    {
>>      if(lastTest())
>>        break loopLabel;
>>      else
>>        continue  loopLabel;
>>    }
>>  }
>> }
>>
>> The reason is that loopLabel is used once for each iteration of the 
>> foreach, which is unrolled. Seeing as labels have functions scope, 
>> this is an error.
>>
> [snip "Duff's Device"-like workaround]
>>
>> A better solution would be to define that labels have function scope 
>> from a syntactic standpoint, meaning that the first code would be 
>> valid because, while the labels references more than one location in 
>> the final program, it only occurs onces in the code. This would be 
>> somewhat bad but only because you can't jump from one iteration to the 
>> next (IIRC the switch/case/goto case can).
> 
> I'd like this to work, but for any identifiers (labels, variables, 
> aliases, whatever). Whatever is declared in a 'static' foreach body 
> should be local to that iteration of it, because AFAICT it's pretty much 
> guaranteed to be an error or bug otherwise.

NO! Definitely not true. Suppose you want to create an alias for the 
first 'int' item in a tuple. You don't know which iteration will create 
the alias.

I've made use of the current behaviour, even with labels. It allows you 
to write things like:

foreach(...) {
  static if (somecomplexcondition) {
    LabelX:
     ...
  }
   static if(someothercondition) {
     goto LabelX;
  }
}
You can create a state machine in this way; you need to be able to jump 
from one foreach iteration into another one.