OOP344 Week 2 - Addition, Subtraction, Multiplication and Division Programs

Addition Program

#include <cstring>
#include <cstdlib>
#include <cctype>
#include <iostream>

using namespace std;

bool validateInt (const char* value){
 bool valid = true;
 int i;
 int len = strlen(value);
 
 if (isdigit(value[0]) || value[0] == '-' && len > 1){
  for (i =  1; i < len && valid; i++){
   if (value[i] < '0' || value[i] > '9'){
    valid = false;
   }
  } 
 }
 else {
  valid = false;
 }
 return valid;
}

int main(int argc, char* argv[])
{
 int num1;
 int num2;
 bool valid = false;

 if (argc == 3){ 
  valid = validateInt(argv[1]) && validateInt(argv[2]);
 }

 if (valid){
  num1 = atoi(argv[1]);
  num2 = atoi(argv[2]);
  cout << "The sum is " << num1 + num2 << endl;
 }
 else {
  cout << "Error: invalid input" << endl;
 }
 return 0;
}

Before compiling the following programs, please copy the validateInt() function in the addition program and paste it before main().

Subtraction Program

#include <cstring>
#include <cstdlib>
#include <cctype>
#include <iostream>

using namespace std;

int main(int argc, char* argv[])
{
 int num1;
 int num2;
 bool valid = false;

 if (argc == 3){ 
  valid = validateInt(argv[1]) && validateInt(argv[2]);
 }

 if (valid){
  num1 = atoi(argv[1]);
  num2 = atoi(argv[2]);
  cout << "The difference is " << num1 - num2 << endl;
 }
 else {
  cout << "Error: invalid input" << endl;
 }
 return 0;
}

Multiplication Program

#include <cstring>
#include <cstdlib>
#include <cctype>
#include <iostream>

using namespace std;

int main(int argc, char* argv[])
{
 int num1;
 int num2;
 bool valid = false;

 if (argc == 3){ 
  valid = validateInt(argv[1]) && validateInt(argv[2]);
 }

 if (valid){
  num1 = atoi(argv[1]);
  num2 = atoi(argv[2]);
  cout << "The product is " << num1 * num2 << endl;
 }
 else {
  cout << "Error: invalid input" << endl;
 }
 return 0;
}

Division Program

#include <cstring>
#include <cstdlib>
#include <cctype>
#include <iostream>

using namespace std;

int main(int argc, char* argv[])
{
 int num1;
 int num2;
 bool valid = false;

 if (argc == 3){ 
  valid = validateInt(argv[1]) && validateInt(argv[2]);
 }

 if (valid){
  num1 = atoi(argv[1]);
  num2 = atoi(argv[2]);

  if (num2 != 0){
   cout << "The quotient is " << num1 / num2 << endl;
  }
  else {
   cout << "Error: cannot divide by 0" << endl;
  }
 }
 else {
  cout << "Error: invalid input" << endl;
 }
 return 0;
}

OOP344 Week 2 - Environment Variable Content Search Program

#include <cstring>
#include <iostream>
using namespace std;
#define MAX 50

int main( int argc, char* argv[], char* env[]){
 char searchStr[MAX + 1];
 char envSubStr[MAX + 1]; 
 int key = -1;
 int i;
 int searchStrLen;
 char* envContent = NULL;

 if (argc == 2){ 
  //make a copy of first argument passed and append an = sign
  strcpy (searchStr, argv[1]);
  strcat (searchStr, "=");
  
  searchStrLen = strlen (searchStr);
  searchStr [searchStrLen] = '\0';
  //binary search
  for (i = 0; env[i] && key == -1; i++){
   strncpy (envSubStr, env[i],searchStrLen + 1);
   envSubStr[searchStrLen] = '\0';
   if ( strcmp (envSubStr, searchStr) == 0){   
    key = i;   
   }  
  } 
 }
 
 if (key != -1){
  envContent = env[key] + searchStrLen;
  cout << envContent << endl;
 }
 else {
  cout << "Not found" << endl; 
 } 
}

OOP344 - Object Oriented Programming II using C++

This semester, I am taking a course at Seneca College called OOP344 -  Object Oriented Programming II using C++. For those who never took computer programming courses at Seneca, OOP344 is an intermediate C++ course with an emphasis on open source programming.

During the first week of OOP344, my professor demystified the pointer. Having studied Java in high school, I never liked using pointers in my code. Hopefully, I will start to appreciate pointers and it's various applications before the end of the semester.