glenn@synaptx.Synaptics.Com (Glenn Gribble) (10/15/90)
I want to make an extensible type-safe function. A simple example would be a type-safe printf(). There are a few problems: 1) Storing the type information with the argument. 2) Dealing with variable length arguments. 3) Allowing a user to add more _safe_ types without recompiling. The closest I have gotten is to make a function that takes a "class varg&" argument. A "varg" can be constructed from an integer or whatever other kind of type is _safe_. The "varg" contains all the type dependant functionality. The big problem is that I can not increase the number of ways I can make a "varg" without changing the header file for the "varg" class. I would like to be able to declare an operator like this: varg operator varg(double d); typedef varg& vargRef; varg& operator vargRef(double d); When compiling this, I get "operator varg : not a member" errors. Does anybody have any clues how to solve this problem? Please note: This has not a discussion about printf. Please tell me I want to use the streams package via email. :-) I am including a simple example that demonstrates my approach. #include <stdio.h> class argBase { public: virtual void printMe() = 0; }; class intArg : public argBase { public: int value; virtual void printMe() { printf("%d", value); } intArg(int x) { value = x; } }; class varg { argBase *b; public: void printMe() { b->printMe(); } varg(int x) { b = new intArg(x); } }; // These do not compile // varg operator varg(double d); // typedef varg& vargRef; // varg& operator vargRef(double d); void safePrintf(const char *fmt, varg& arg1) { for ( ; *fmt != '\0'; fmt++) if (*fmt == '%') arg1.printMe(); else putchar(*fmt); } main() { safePrintf("This is simple example #%\n", 1); } -- Glenn Gribble glenn@synaptics.com uunet!synaptx!glenn