Re: augmented operators (was: implicit parameters)

[Edgar Toernig <froese@...>]

Hi,

Nick Trout wrote:
> 
> Have you though about adding augmented operators eg. +=, -= etc in Sol?

I guess every C programmers comes to the point to think about
this ;-)  But I came to the same conclusion as the Lua team:
I do not plan to add them to Sol.  IMHO it's not worth the
trouble.

The only good thing an them is that it's a little bit shorter
to write.  On some occasions it may even be much shorter.  But
besides that it gives nearly nothing except a more complicated
system.  And some constructs would be just weird and give no
_obvious_ results (ie "a,b += c" is what?).

One may think that it could be faster to execute.  But it isn't
if you want the semantic of "a += b" is "a = a + b" (with "a"
evaluated only once).  There are two types of storage in Lua/Sol:
tables and locals.  For tables you have to perform the two
accesses to the table (read and write) because of possible tag-
methods (get/settable).  Nothing to optimize here.  Locals could
be optimized with a special instruction but again you have to
consider tag methods for "+" and that reduces the possible
optimization to <numlocvar>+=<num> [1].

One could try to make += and co special operators (ie "incr_by",
"mul_by", ...) with appropriate tag methods.  But that requires
references to objects and these only exist for tables, not for
locals.  (Btw, the same problem exists for "++" and "--".)
Beside that it would make the language more complicated.

Result: you would only get some very expensive syntactic sugar ;)

Ciao, ET.

[1] This case could be optimized even without the special
syntax.  But I think it won't be noticeable in any reasonable
application so I'm not trying to do this at the moment.  But
if somebody has a nice patch for this ...