Re: "PORTING C" > How to assign a value to a define statement?
Robby wrote:
"Igor Tandetnik" wrote:
So, forget about implementation details. Design the interface from =
the client's >point of view: if you somehow magically had a
thrid-party library of your dreams >doing precisely what you want to =
do, what would that library's API look like? What >calls
would you make to it? Then, once you have your ideal interface, fill =
in the >implementation.
Its just a matter of calculating the values we saw earlier and =
assigning the
result to CURR_SYS_OSC and making it global..... but there are dozens =
of
ways to do this.... is it better to call a function and use the macro =
in
there , like this:
=
==========================
==========x.c
main()
{ int CURR_SYS_OSC;
CURR_SYS_OSC = compute_sys_osc(8.0, 2.0, 21.0, 8.0);
SYSTEMConfig(CURR_SYS_OSC, SYS_CFG_ALL);
}
int compute_sys_osc(extCrys, fpllidiv, fpllmul, fpllodiv)
{
int FREQ;
FREQ = COMPUTE(extCrys, fpllidiv, fpllmul, fpllodiv);
return FREQ;
}
=
==========================
=========
But if I do this, CURR_SYS_OSC is not available to other modules that =
might
need it.
How about breaking it into two calls:
set_sys_osc(parameters_here);
get_sys_osc();
Have set_sys_osc store the computed value in a file-level static =
variable, for example, in the source file where these two functions are =
defined, and get_sys_osc return that variable. No macros needed.
Also, CURR_SYS_OSC would not be available for the OSC_PERIOD #define
statement. So I think, the above code is not an object oriented =
approach!
I'm not sure what "object oriented" has to do with this problem. In any =
case, piling on ever more macros is certainly not the one true way to =
the OOP nirvana.
So what you are saying is that this is an API function:
void f1()
{
// does something!
}
If it is part of a collection of related functions, then why not. "API" =
doesn't mean anything special at the language level - there's no keyword =
or anything to mark a function as being "API". It's just a way to think =
about organizing software.
now, is config_obj() an API or just a simple function used to =
innitialize
the values of an object?
Again - API is a collection of related functions. It's meaningless to =
ask whether one isolated function is "an API".
--
With best wishes,
Igor Tandetnik
With sufficient thrust, pigs fly just fine. However, this is not =
necessarily a good idea. It is hard to be sure where they are going to =
land, and it could be dangerous sitting under them as they fly overhead. =
-- RFC 1925