2.3 Create the main function

Every C++ program must define an entry point in the form of a main function .

Delete the existing file strom.cpp (right-click its name in the Solution Explorer, then choose Remove). Create a new file main.cpp (right-click Source Files folder, then choose Add > New Item…, click C++ File (.cpp)) and add the following code to it, saving the file when done.

#include <iostream>	
#include "node.hpp"
#include "tree.hpp"

using namespace strom;

const double Node::_smallest_edge_length = 1.0e-12;

int main(int argc, const char * argv[]) {
    std::cout << "Starting..." << std::endl;
    Tree tree;
    std::cout << "\nFinished!" << std::endl;

    return 0;
}	

Explanation of main.cpp

Recall that the data member _smallest_edge_length in the class Node was declared to be static, so we must initialize it in a source code file, and main.cpp is our only source code file, hence the line that sets _smallest_edge_length to the very tiny value 1.0e-12.

The main function firsts announces that the program is starting to run (by displaying Starting... to standard output), then creates a Tree object having nodes made of Node objects, then announces that the program is finished running just before returning 0 (the exit code 0 tells the operating system that the program ended normally).