Re: Remove all do_inplace* logic from C++

[John W. Eaton]

On 05/16/2013 01:32 AM, Olaf Till wrote:
> On Wed, May 15, 2013 at 11:36:46AM -0400, Jordi Gutiérrez Hermoso wrote:
> > <snip>
> > Any objection to completely removing all of the inplace logic from C++?
>
> What is if the lhs operand (m-code) contains, e.g., indexing
> operations? E.g.
>
> a(id1, id2, id3) += b;
>
> against
>
> a(id1, id2, id3) = a(id1, id2, id3) + b;
>
> or even
>
> c{id4, id5, id6}(id1, id2, id3) += b;
>
> against
>
> c{id4, id5, id6}(id1, id2, id3) = c{id4, id5, id6}(id1, id2, id3) + b;
>
> or even more complicated?
>
> Have you checked whether Octaves do_inplace code you speak of is able
> to spare the double evaluation of the index operation? If it is, this
> would be surely more than an optimizing compiler could achieve,
> wouldn't it?

No, the code Jordi is looking at is at a much lower level than indexing 
operations in the scripting language.

The A op= B operators in Octave are nothing more than syntactic sugar. 
They are always exactly equivalent to A = A op B.

jwe