Replacing the comma operator

[Andrei Alexandrescu]

Stewart Gordon wrote:
> Andrei Alexandrescu wrote:
> <snip>
>> No, sorry. Usually I strive to be precise, but this time I just 
>> wasn't. The plan is to define order of evaluation to be lexical order. 
>> Somehow I can't convince Walter that that means assignment too!
> <snip>
> 
> I still would like to know where you found that plan!
> 
> The decision to leave order of evaluation unspecified was a deliberate 
> one at the time, and for good reasons.
> 
> One of these reasons was to open the option of evaluating subexpressions 
> in parallel.  I'm not sure what the others were, but another 
> optimisation potential that comes to my mind is to minimise the working 
> memory while still allowing expressions to be written in an intuitive 
> order.
> 
> Who has decided that these reasons are no longer good, and why?

This has been a source of long discussion in C++ circles, and Walter and 
I have also discussed the matter several times. Defining order of 
evaluation has good benefits, and the loss in efficiency has with time 
been reduced to just a few corner cases that don't seem to justify the 
cost anymore. Note that operations can still be evaluated in parallel as 
long as there's no dependencies between them.

Andrei