Re: [boost] [proto] transforms && rvalue refs

Subject: Re: [boost] [proto] transforms && rvalue refs
From: troy d. straszheim (troy_at_[hidden])
Date: 2009-03-30 13:30:58

Joel Falcou wrote:
> troy d. straszheim a écrit :
>>
>> When it is time to evaluate the expression, the grammar fires the 
>> transform for exp(B) first.  It creates a temporary T with the same 
>> dimensions as B and and a function is called to compute the result 
>> into T.  Now 'T * C' happens.  In this case there is an available 
>> temporary, 'T', so the result can go right in to T.  T is returned and 
>> moved in to A.  Done...  at least, that's the idea.
>>
> No, when you evaluate the expression, you iterate via a for loop nest 
> over the elements of all array, recursively calling the elementwise 
> version of exp and *. The context just evaluate one element at a time. 
> In the end, the only temporary created are those from the elementwise 
> function return.

That's the point...   you can't do that here.   The elements behind A B 
and C are on the other end of a very slow bus.

-t