C. Implementation of functions with uncertain number of parameters

In some cases, you can determine the number of parameters of the function as needed. Typical examples include the familiar functions printf () and scanf.

So how are they implemented?

The C compiler usually provides a series of macros to handle this situation to shield the differences caused by different hardware platforms and increase program portability. These macros include va_start, va_arg, and va_end.

The following is an example of using the above function to write at will:

# Include "cstdarg" # include "iostream" using namespace std; // type of the c parameter. The number of parameters is unknown. // Custom method int Sum (int Num ,...) {int S = 0, T; va_list ap; va_start (ap, Num); for (int I = 0; I