function to determine the largest of three numbers (double)

// function to determine the largest of three numbers (double)
double largest_of_three ( double x, double y, double z )
{
    double largest(0);
    if( (x>=y) && (x>=z) ) {largest = x;}
    else if(  (y>=x) && (y>=z) ) {largest = y;}
    else largest = z;
    return largest;
}