CS 131 - Week 12, Lecture 1
(but Thursday, November 11 is Veteran's Day holiday)

C++ program:
*  a C++ program consists of a function named
   main and whatever other functions and/or
   classes and/or other beasties are used in
   that program

*  when this collection of functions is compiled,
   linked, loaded, and turned into an executable
   file -- then when this executable file/executable
   program is run, the main function's actions are
   done; (and it may call other functions, which
   may in turn call other functions, and so on...)

   ...but the action starts at main;

*  according to Wikipedia: (looked up in 2007)
   the following 3 headers are OK for this main
   function:
   int main(void)
   int main()
   int main(int argc, char* argv[])

*   what is that int?
    *   for CS 131, your main functions should return
        one of the named constants which you
	happen to get by #include'ing iostream

        EXIT_SUCCESS 
        EXIT_FAILURE

*   typically, in here, the basic main skeleton
    (so far) would be:

// save this in a file with suffix .cpp 
// whose name is (by convention) the name you
// want for the final executable file

/*-----
 signature: main: void -> int

 purpose: either:
          <describe the program being written> OR
          testing program for the function/class blah

 examples: <describe, in prose, the effect of running
           this main>

 by: 
 last modified:
-----*/

#include <iostream>
#include <string>
#include "blah.h"
using namespace std;

int main()
{
    // do stuff
    return EXIT_SUCCESS;
}

*   a few words about #include

*   # means it is a pre-processor directive;  
    #include really copies in the contents of
    of the file specified, 
    and then compilation proceeds...

    *   for C++ standard libraries, in ANSI-standard
        C++, you put just the name of the library
        in angle brackets:

#include <iostream>
#include <string>
#include <cmath>

    *   for functions or classes you have written 
        and want
        to use in another function, and that
        are in the same directory as this function
	(or in a standard path of some sort...)
    
        write the .h file's name in double quotes

#include "boa.h"
#include "tank_volume.h"

   *   we are, by default, using the standard
       namespace -- so, by the C++ ANSI standard,
       we will conclude our list of #include's
       with:

using namespace std;

*   let's write a main using the main_template
    that'll try out sum_array from Friday;
    I'm going to call this:
    try_sum_array.cpp

*   how do you turn a collection of C++ functions (one of which has the
    name main) into an executable program?

    ... you compile and link them together.

   (you must put ALL the functions involved in the program in the
   compile-and-link command!!)

   g++ funct1.cpp funct2.cpp ... main_funct.cpp -o program_name 

   or

   g++ funct1.o funct2.o ... main_funct.o -o program_name 

   (if you JUST want to compile a function, main or not, JUST type

   g++ -c funct.cpp

   ...it produces a .o file)

   *   C++ STYLE (course style too):
       name the file with the main function the name you'd
       like the program to have

       g++ program_name.cpp funct_used.cpp -o program_name 
           ^ main is in here

*   void functions

    some functions just don't return anything;
    they have a side-effect, and they're done;

*   like a void method (like our modifier methods),
    these have a return type of void

void my_void_function()

    *   like a void method, they don't need
        a return statement

    *   (but you CAN have a return with no expression
        following it --
return;
        ...although we usually won't)