Super-dee-duper D features

[Dave]

Andrei Alexandrescu (See Website For Email) wrote:
> Sean Kelly wrote:
>> Andrei Alexandrescu (See Website For Email) wrote:
>>> Frits van Bommel wrote:
>>>> Andrei Alexandrescu (See Website For Email) wrote:
>>>>> Bill Baxter wrote:
>>>>>> Yeh, I don't get it either.  How would that help me implement 
>>>>>> merge() from merge sort for instance?
>>>>>
>>>>> Merge bumps the iteration in both collections conditionally. The 
>>>>> form above bumps the iteration in the two collections 
>>>>> unconditionally, until one is finished; then it continues with the 
>>>>> other until that is finished.
>>>>
>>>> In other words, it doesn't :(.
>>>
>>> A need for loops iterating over multiple collections depending on 
>>> arbitrary conditions will always be there. The point of extending 
>>> foreach is to address the often-encountered case when you want to 
>>> iterate over multiple collections simultaneously (e.g.: copy a 
>>> collection to another), just like foreach itself is addressing the 
>>> particular but frequent case of iterating one collection in a linear 
>>> manner.
>>
>> What about:
>>
>>     foreach (i ; coll1) (j ; coll2)
>>     {
>>         if( true )
>>             continue i;
>>     }
>>
>> ie. allow 'continue' to accept labels to specify which collection is 
>> iterated.  A 'continue' without labels would iterate both.
> 
> I think that's a great idea, except that "continue to label" has the 
> same syntax: http://digitalmars.com/d/statement.html#ContinueStatement
> 
> Andrei

How about using 'next' to keep it simple, so the compiler doesn't have to create / check for 'i' and 
'j' as lables with the same function scope:

i:  while(...)
     {
        foreach (i ; coll1) (j ; coll2)
        {
            if( true )
                continue i;
            if( i < j )
                next i;
        }
     }
?