Modular Programming

[HectorDiaz]

Hello, I am having issues with my Data Structures lab and I was wondering if you guys could help me.

Here is the lab:

Write a program that asks for two numbers as arguments, multiplies them, and prints out the product and the two numbers. Call your executable, multiply; it operates like, for example,

multiply 3.14 57

If a wrong number of arguments or wrong types are supplied, it should display a message informing the user how to use the program correctly.
Your program must be made up of three modules, namely, main.cpp ( for handling the arguments ), product.cpp ( for calculating the product ), and print.cpp ( for printing out the product ). Check if each of the modules can be compiled properly by the command,

g++ -c program_name.cpp

Finally, write a Makefile that contains all the compilation processes to generate the executable multiply. The Makefile should have a clean instruction so that when one executes,

make clean
the object files will be deleted.

End lab

Here is what I know and would like to find out

Know:

How to write a program that accepts command line arguments, multiplies them and shows the result

I have to break up the program into 3 objects and link them using the compiler

Would like to find out:

How would i go about splitting the program?(Without using a header file)

I understand the concept of the Makefile, but don't understand the writing of one

Here is the code i wrote that is working

#include <iostream>
#include <string>
#include <sstream> 
#include <cstdlib> 

using namespace std;

int main(int argc, char *argv[])
{
	if (argc <= 1)
	{
		if (argv[0])
		{
		    cout << "You did not provide an argument\n";
		}
		exit(1);
	}
	
	double multiple = 1.0;
 
    for(int i = 1; i < argc; i++)
	{
	    stringstream convert(argv[i]); 
 
	    double currentArg = 0.0;
	
    	//should the conversion fail
    	if (!(convert >> currentArg)) 
    	{
    	    currentArg = 0;
    	    cout << "Please enter only numerical values and I will show the product\n";
    	    exit(1);
    	}
    	
    	multiple = currentArg * multiple;
    	
	}
	
	cout << "Your multiple is " << multiple << "\n";
 
	return 0;
}

I tested it with multiple values and tried throwing some curveballs and it worked out fine.

Thank you!

[dhayden]

As a next step, you should create the functions that will eventually go into separate files. One function should multiply 2 numbers and the other should print the result.

The code in this assignment is pretty trivial. It seems to me that the real purpose is to get you acquainted with multiple cpp files and the construction of a makefile.