On Tue, Nov 16, 2010 at 11:44 AM, Jan Hudec <b...@ucw.cz> wrote:
> On Tue, Nov 16, 2010 at 18:51:12 +0100, Günther Wutz wrote:
>> It is possible to use cpp as Preprocessor. I'm working on a
>> wrapper-program to combine cpp and give it valac to compile. The easiest
>> way i found actually.
>
> Sorry. That's an extremely bad idea for most cases.
>
> The easiest way is to tell vala to emit the symbols that will then be defined
> when compiling the generated C code. That way vala will guard you from name
> conflicts and the code will be more readable.
"preprocessor" is probably a bad word as it makes people think about
C-style preprocessor. If I understand the request correctly one wants
"compile-time type-safe constants substitution".
> In C, the preprocessor is generally used for two things:
> - symbolic constants -- but real constants serve the purpose better and
But what if you want to change the real constant value at the
compile-time? A classical example is DEBUG vs OPTIMIZED mode. During
development I want to log of information to stdout, like this:
if (DEBUG) {
stdout.printf("User ID is: $user");
}
and I don't want to have this code in the release version. To make it
happen one can use something like
bool DEBUG=false;
and compile the vala program with -DDEBUG (or its equivalent
-DDEBUG=true). This compiler flag changes the default value of the
const.
Type-safety means that vala compile knows that DEBUG is boolean and
complains if someone tries to use number/string here (-DDEBUG=foo) or
tries to set value for unexisting constant.
> - generic constructs -- but vala does have generics, so you don't need
> those.
> Even in C++ you usually avoid the preprocessor for most things, because
> preprocessor symbols cannot be scoped. Which is doubly so applicable to vala.
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