Re: undefined compound chaining behavior

[Mike Miller]

On Tue, Jun 10, 2014 at 08:09:40 +0330, Hossein Sajjadi wrote:
> accoring to the manual:
> expr1 op= expr2
> is evaluated as
> expr1 = (expr1) op (expr2)
>
> so the expression
> a=1;
> a+=(a+=4);
>
> should be equivalent to
> a=1;
> a=a+(a=a+4);
>
> but the firt expression results 10  and second results 6

Ok, I understand. I think the best thing you can do to resolve this is
to report a bug [1] requesting that the manual be updated to describe
this behavior of assignment operators more clearly. To be clear, there
is no undefined behavior here, it's just that OP= means that the
left-hand side of the assignment is evaluated when the assignment is
made. So the simple equivalence described in the manual is not correct
if EXPR2 modifies EXPR1 as a side effect.

[1] https://savannah.gnu.org/bugs/?func=additem&group=octave

Thanks,

-- 
mike