Re: [Adobe-source-devel] Questions about sheet_t::implementation::get

[cee1 <fy...@gm...>]

Hi Sean,

Thanks for the replay.
I'm reading code of ASL 1.0.42.

> In the function sheet_t::implementation_t::get:
> (adam.cpp 1387) "if (initialize_mode_m) { ..."
> I've found initialize_mode_m is false when instantiates
> sheet_t::implementation_t, and will be true when calls add_constant,
> add_input or add_interface. So the following assert should always fail:
>
>
> (line 1435 in my copy) When a sheet is constructed, initializers are
> evaluated as  the cells are added. the get() function is called by the
> expression evaluator to look up variables. The expressions on a sheet
> initializer can only refer to cells that have been previously declared
> (added to the sheet) and the initializers don't attempt to follow
> relationships, they only pick up the cell value of previously initialized
> cells.
>
> Is "sheet_t::implementation_t::get" (only) directly used in the following
line? (i.e. when an interface cell has no define expression):
  799.        cell_set_m.push_back(cell_t(access_interface_output, name,
  800.
 boost::bind(&implementation_t::get, boost::ref(*this), name),
  801.                                    cell_set_m.size(),
&cell_set_m.back()));


> (adam.cpp 1428) assert(cell.interface_input_m && ...),
> Because when this line is reached, the initialize_mode_m is false, then we
> should not have called add_constant, add_input or add_interface, so the cell
> is not an interface cell, assert failed.
>
>
> (line 1476) - there is a return statement on line 1449 so this line is not
> going to be reached if initialize_mode_m is true.
>
> I found initialize_mode_m is true when:
  a) reinitialize is called
  b) add_constant is called
  c) add_input is called
  d) add_interface is called
No place except constructor of sheet_t::implementation_t set
initialize_mode_m false.

The line 1476: assert(cell.interface_input_m && "FATAL (sparent) : Only
interface cells should be on the get stack.");
That means we expect an interface cell here, but if we have an interface
cell, it should be added by add_interface, then initialize_mode_m should be
true: this line is not reachable ?

>
> Also, I find some code that makes no sense to me, like:
> (adam.cpp 1267) sheet_t::implementation_t::initialize_one
> accumulate_contributing_m.reset();
> ...
> cell.init_contributing_m |= accumulate_contributing_m;
>
>
> (1315) accumulate_contributing_m is a member variable that holds a bit
> field corresponding to cells. Executing calculate_m() on line 1323 is going
> to set the bits for the cells that are read as part of that expression in
> accumulate_contributing_m. Then on line 1325 that bit set is or'ed with the
> other bits contributing to the initializer on that cell.
>
> In many places, calculate_m is a binding function object which is
essentially implementation_t::calculate_expression -- this function doesn't
touch accumulate_contributing_m.
But calculate_m can also be a binding function object which
is essentially implementation_t::get -- this function
touches accumulate_contributing_m.
Am I right?

>
> or
>
> (adam.cpp  1173) in function sheet_t::implementation_t::update
> if (cell.specifier_m == access_interface_output)
> get_stack_m.push_back(std::make_pair(cell.name_m, false));
>
>
> (1221) The get_stack_m is used to detect self-referential expressions in
> get() (which is called as part of calculating an expression for variable
> lookup). For example, if you have a rule like:
>
> a <== max(a, b);
>
> Then the lookup of "a" is self referential, and must refer to the initial
> value of "a", but "b" is not self referential and will refer to the final
> value of "b".
>
> See line 1475 for where this is used.
>
> ...
> if (cell.specifier_m == access_interface_output) get_stack_m.pop_back();
>
>  Does that means sheet_t::implementation_t::get may be called recursively?

>
>
> Sorry for this mass mail, but I feel lost in adam.cpp. Could someone show
> me the global picture of how these functions in sheet_t::implementation
> work?
>
>
> No problem - keep the questions coming.
>

Thank you.


Regards,
- cee1