Question

I have implemented printf for vector type. The values in vector type are represented as (element1,element2,…) For example for vector of size 3, a possible value could be (1,2,3)

My implementation for printf is:

int my_printf(const char *format,...)
{
    va_list args;
    int argSize = 1; // get the number of elemts in vector
    const char* vec;
    vec = strchr(format,'v');
    if(vec != NULL)
        argSize = atol(vec + 1);
    va_start (args, format);
    int i = 0,ret = 0;

    do // print all elements
    {
        ret = vprintf ("%d ", args);
        fflush(stdout);
        va_arg(args,float);
    } while(i < argSize);
    va_end (args); 

    return ret; 
}

int main()
{
    my_printf("v3",(10,12,13));
    return 0;
}

While va_start (args, format); args gets value 13 prints it and for the next two printings prints 0 (args = 0)
What could be the solution?

Answer 1

(10,12,13) represent the single number 13. It’s comma operator, quite peculiar feature of C language.

So your code is equivalent to this:

int temp = (10,12,13); // now temp == 13
my_printf("v3", temp);

In C, there is no vector type as it’s known from C++. There are only arrays. You could initialize array like this:

int array[] = {10, 12, 13};

–and use the array as an argument for my_printf.