OpenEuphoria

Re: question

• Posted by Derek Parnell <ddparnell at bigpond.com> Nov 16, 2004
• 523 views

Tone Škoda wrote:
> 
> Derek Parnell wrote:
> > 
> > Yes, 'data' would have been copied when the append was done because
> > after the append, 'data' contains different values from 'tmp[2]'. But
> > til that point, there would have only been one copy of the data in RAM.
> > 
> > If you do 'tmp={}' I think that this will add the RAM that tmp was
> > using to the pool of RAM that Euphoria can reuse for this application.
> > 
> > If you are running this as a Windows app, I also think that the released
> > RAM may also be available for other apps too.
> 
> What would happen when when I would do 'tmp={}' before I modify 'data'? Would
> there
> be any copying going on? Because if yes, interpreter at would have to do these
> two
> things: 1) delete memory of 'tmp' 2) allocate memory for 'data'. And these two
> memories
> would contain same data.

procedure main ()
 sequence tmp
 sequence data
 tmp = f () -- tmp refers the sequence data returned by f(),
            -- and this point that is the only reference to it.

 data = tmp [2] -- data refers to tmp[2]

 tmp = {} -- tmp drops reference to f() return sequence, but the
          -- sequence's contents are not deleted 'cos of the
          -- refers to the 2nd element.
 -- There is some 'expansion' space defined at the end of a newly
 -- created sequence. So this append would most likely not 
 -- cause a copy to happen but the expansion area would shrink.
 data = append (data, "something")
 -- So the original sequence returned by f() is still in RAM
 -- and there probably hasn't been any copying done.
 ...
end procedure 

If you don't do the "tmp = {}" then the append would have to make 
a copy of the contents because 'tmp' would still be referring to
it.

> This is one thing because of which I am thinking of switching to C, because
> there you
> have pointers and things like this are crystal clear.

Yes, but the responsibility is on you and your perfect code
to always "get it right". That is why I stay away from C.


BTW, this is all speculation as to how Eu works because I haven't
actually examined the source code of the Interpreter.

-- 
Derek Parnell
Melbourne, Australia