#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
#include <stdarg.h>  // va_list, va_start(…), va_arg(…), va_end(…)
// Must include stdarg.h for variadic function

// VARIADIC FUNCTION to add an arbitary number of numbers.
// - Variadic functions let you accept an arbitary number of parameters.
//   - Variadic function must take at least one parameter
// - Arguments may be of different types.
// - You may call va_arg only as many times as there are additional arguments.
//   - mintf("…");           // do not call va_arg(…) at all
//   - mintf("…", A);        // call va_arg(…) exactly one time.
//   - mintf("…", A, B);     // call va_arg(…) exactly two times.
//   - mintf("…", A, B, C);  // call va_arg(…) exactly three times.
// - Additional arguments are not an array
//   - You cannot access the i'th element arbitrarily.
//   - Wouldn't work since the types may vary.
// - Additional arguments must be accessed…
//   - in order
//   - in a single pass
//   - starting from the first additional argument (if any)

// ASSUME the caller follows the rules given in the documentation for the function.
// - For public functions in this class (i.e., given in the requirements), the spec
//   is the document.
// - For these examples here, the comment is the document.

int sum(int n_first, ...) { // ... means and 0 or more parameters.
         // ↑
         // last named parameter is n_first
    // sum(…) returns the sum of the arguments.
    // - last argument must be 0.  That signifies the end.

    va_list more_args;  // more_args is a name that you can choose.
    va_start(more_args, n_first);  // va_start(«va_list object», «last named parameter»);
    int arg = n_first;
    int sum_of_args = arg;
    while(arg != 0) {
        arg = va_arg(more_args, int);
        // va_arg(«va_list object», «expected arg type»).

        sum_of_args += arg;
    }
    va_end(more_args);  // clean up (to avoid memory leaks, etc.). (penalty if you forget)
    return sum_of_args;
}

int main(int argc, char* argv[]) {
    printf("sum(0) == %d\n", sum(0)); //////////////////// Step 1 (TDD)
    printf("sum(5, 0) == %d\n", sum(5, 0)); ////////////// Step 2
    printf("sum(5, 7, 0) == %d\n", sum(5, 7, 0)); //////// Step 3
    printf("sum(3, 5, 7, 0) == %d\n", sum(3, 5, 7, 0)); // Step 4
}
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