 |
lua-l archive |
|
|
||
|
|
I wonder if anyone can help me with the following
questions. I am trying to add metamethods like _add and __mul to a lua class (a
table configured in the appropriate way). Each of these arithmetic
metamethods must return a new object. For example, suppose B and C are
objects and I use
A = B + C
The result A is a new object, which is fine. I
can delete A and grab its memory whenever I want to. Now what if I use an
_expression_ like the following?
A = (B + C - D) / D - F*G ^
H
There are a whole bunch of intermediate objects
created as each operator is processed, but I can never get to them to delete
them. When do they get garbage collected? Is it automatic, right after the
_expression_ is evaluated?
That's the first question.
Related to that is a second question. The
class holds a pointer to a C++ object. So, when the table (class) gets
gc'd, it needs to delete that C++ object as well.
I've gone back and forth in the blue book trying to
understand this and I just don't get it from the discussion and the examples. I
can see that *something* has to have a metamethod __gc which calls a Cfunction
with userdata containing the C++ pointer. But the question is the linkage
between all these things. I just don't see what to do. Whenever lua tries
to collect the table, I want it to call a Cfunction with the pointer that
should be deleted.
Michael
|