Chapter 3.4: Function Prototypes

Adapted from: “Object-Oriented Programming Using C++” by Ira Pohl (Addison- Wesley)

Program that demonstrates function prototypes in C++¶

// Add three ints - illustrating function prototypes
#include <iostream>

int add3(int, int, int);
double average(int);

using namespace std;

int main()
{
    int score_1, score_2, score_3, sum;

    cout << "\nEnter 3 scores: ";
    cin >> score_1 >> score_2 >> score_3;
    sum = add3(score_1, score_2, score_3);
    cout << "\nTheir sum is " << sum;
    cout << "\nTheir average is " << average(sum);
    sum = add3(1.5 * score_1, score_2, 0.5 * score_3);
    cout << "\nTheir weighted sum is " << sum << ".";
    cout << "\nTheir weighted average is " << average(sum) << "." << endl;
}

int add3(int a, int b, int c)
{
    return (a + b + c);
}

double average(int s)
{
    return (s / 3.0);
}

Compile and Execute the Program¶

The above program is compiled and run using Gnu Compiler Collection (g++):

import os
root_dir = os.getcwd()

code_dir = root_dir + "/" + "Cpp_Code/Chapter_3_4_Function_Prototypes"

ch_dir_stat = os.chdir(code_dir)

build_command = os.system("g++ add3.cpp -w -o add3")

exec_status = os.system("echo \"10 20 30\" | ./add3")


Enter 3 scores: 
Their sum is 60
Their average is 20
Their weighted sum is 50.
Their weighted average is 16.6667.

exec_status = os.system("echo \"1210 8750 54360\" | ./add3")


Enter 3 scores: 
Their sum is 64320
Their average is 21440
Their weighted sum is 37745.
Their weighted average is 12581.7.