On 2013-02-01 11:34, timotheecour wrote:
One of the rare features I miss in C/C++ is stringification macro using "#x":--- #include ... #define DEBUG(x) disp_val(#x,x) template<typename T> void disp_val(const char*name, const T& x) {std::cout << name << "=" << x;} int main(){ DEBUG(1+2); //will print 1+2=3 (and we can add line, file and func info) ASSERT(1+2==4); //can also be defined such that it'll print 1+2==4 failed... } --- In D, we have built-in assert message that'll print the failing expression "1+2==4 failed" in case of failure but that's about it: no further processing can be done on that message, and there's nothing we can do about the DEBUG(1+2) case. I did a function that requires one to write mixin(myDebug("1+2")); but that's not as good, especially because of the quoting that makes most IDE's unaware of the syntax inside (maybe monod would work but still...). However there could be a clean D solution that alleviates need for macros: I'd like to add __ARGS__ to the list of __FILE__, __LINE__, __FUNC___: P1) 1st proposal: __ARGS__ is a string representing the comma separated list of arguments passed: void DEBUG(T,A)(T a, A args=__ARGS__){writeln(args,"=",a);} void DEBUG2(T1,T2,A)(T1 a1,T2 a2, A args=__ARGS__){writeln(args);} DEBUG(1+ 2); //will print "1+ 2=3", ie args="1+ 2" DEBUG(1+ 2, 3*3); //will print "1+ 2,3*3" (ie normalize the comma separation) P2) same but __ARGS__ is string[] with one string per argument; the compiler already did the job of parsing, might as well use it: void DEBUG(T)(T a1, T a2, string[] args=__ARGS__){ writeln(args[0],"=",a1); writeln(args[1],"=",a2); } A question: whether or not to include the first argument in a UFCS/member function call ("hello".fun(1+2) ). P3) additionally, create a __CONTEXT__ that is a struct consisting of __ARGS__,__FILE__, __LINE__, __FUNC___. This has been proposed before and makes even more sense now. Additionally, it could give info on whether the call was UFCS'd or not, etc, information which is lost otherwise (I don't think traits could help distinguish which version was called, a.fun(b) or fun(a,b)).
Sounds like an ugly hack for AST macros. This is a proposal for AST macros I've been working on. It's not finished but here it is:
https://dl.dropbox.com/u/18386187/ast_macros.html -- /Jacob Carlborg
