Trying to learn C++ by myself. C++ simple Calculator.

[drgr33n]

Hey Guys,

Was reading a few posts on here and looks like a cool place to come and try to broaden my knowledge and try and teach myself C++.

I've only been reading a few days and I decided to try and create a simple calculator. I wanted to see if anyone else had done this and when I consulted google this site was one of the first results with the following post ..

http://www.daniweb.com/software-development/cpp/threads/238276

So I decided to try and modify his code to make it loop and return after a calculation was complete. The trouble with my code is if a non numeric key is entered when prompted it goes into a weird loop. I was wondering if someone could take a look and let me know where I'm going wrong ?

Here,s my code ..

// Zarrens C++ Simple Calculator
// I decided to put everything I've learnt in the past few days to
// create this little simple calculator so I can practice my skills 
// as I improve, I will improve my calculator

// Header files
#include <cstdlib>
#include <cstdio>
#include <iostream>

using namespace std;

void Welcome_screen() {
   cout << "Weclome to Zarren's C++ Simple Calculator.\n";
   cout << "This is a little project that I will be improving as I improve ;)\n\n";
}

float number_cruncher(float num1, float num2, char myoperator) {
  float result;
  switch (myoperator) {
    case '+':
      result = num1 + num2;
      break;
    case '-':
      result = num1 - num2;
      break;
    case '*':
      result = num1 * num2;
      break;
    case '/':
      result = num1 / num2;
    break;
    default:
      cout << "You fail";
      break;
  }
  return result;
}

int main() {
  char controller;
  float num1=0;
  float num2=0;
  char myoperator;
  do { 
    Welcome_screen();
    cout << "Enter your first number: ";
    cin >> num1;
    cout << "\nEnter the operator: ";
    cin >> myoperator;
    cout << "\nEnter second number: ";
    cin >> num2;
    float result = number_cruncher(num1, num2, myoperator);
    cout << '\n' << result << "\n";
    cout << "Type any key to contunue or Q to quit ...:";
    cin >> controller;
  } while(controller != 'Q');
  cout << "See ya !!!";
  return 0;

[triumphost]

You want something like

if(!isdigit(num1 || num2)){
   cout<<"You entered a character that is not a digit\n";
   Welcomscreen();
}

And for C++.Net you do:

if(!Char::IsDigit(e->KeyChar) && e->KeyChar != 0x08)//The 0x08 is the backspace key.. you might wanna add 0x0D which is the Enter button.
{
	e->Handled = true;
}

[drgr33n]

Thanks for your reply but unfortunately this didnt help as it goes into a loop if I put a char in num1 so it never reaches the test ?

[sergent]

Normal cin sucks so I midified it and this is are 2 functions I use instead of cin:

int kcin(int i) {
    int variable;
    while(1) {
    if (cin >> variable) {
break;
}
if(cin.fail()) {
cout << "Input Again: ";
cin.clear();
cin.ignore( 1024, '\n' );  //spend a lot of time on this!
}
}
return variable;
}

char kcin(char a) {
    char variable;
    while(1) {
    if (cin >> variable) {
break;
}
if(cin.fail()) {
cout << "Input Again: ";
cin.clear();
cin.ignore( 1024, '\n' );  //spend a lot of time on this!
}
}
return variable;
}

One is to enter a character and the othera variable.
It kinda sucks because you do not send an adress of a variable but a copy of it so you have to return it. I wrote this functions a long time ago and still use them and I don't feel like changing 'em.
You use them like this
int variable=kcin(variable);

char character=kcin(character);
The arguments you pass to the function overload it and because there is 2 different functions if you pass an int to it it will call kcin(int) and if a character kcin(char).

[drgr33n]

Thanks Sergent that's exactly what I needed. I'm not worried about passing the variable by reference as I've only been studying for about a week lol :D

here is my modified code to include your cin function.

// Zarrens C++ Simple Calculator
// I decided to put everything I've learnt in the past few days to
// create this little simple calculator so I can practice my skills 
// as I improve, I will improve my calculator

// Header files
#include <cstdlib>
#include <cstdio>
#include <iostream>

using namespace std;


void Welcome_screen() {
   cout << "Weclome to Zarren's C++ Simple Calculator.\n";
   cout << "This is a little project that I will be improving as I improve ;)\n\n";
}

float input_check() {
  float num;
  while(1) {
    if (cin >> num) {
      break;
    }
    if(cin.fail()) {
      cout << "Numerical value needed !! Try again: ";
      cin.clear();
      cin.ignore( 1024, '\n' ); //spend a lot of time on this!
    }
  }
   return num;
}

float Plus    (float num1, float num2) { return num1+num2; }
float Minus   (float num1, float num2) { return num1-num2; }
float Multiply(float num1, float num2) { return num1*num2; }
float Divide  (float num1, float num2) { return num1/num2; }

int main() {
  char controller;
  float num1=0;
  float num2=0;
  char myoperator;
  float result=0;
  do { 
    Welcome_screen();
    cout << "Enter your first number: ";
    num1 = input_check();
    cout << "\nEnter the operator: ";
    cin >> myoperator;
    cout << "\nEnter second number: ";
    num2 = input_check();
    switch(myoperator) {
      case '+' : result = Plus     (num1, num2); break;
      case '-' : result = Minus    (num1, num2); break;
      case '*' : result = Multiply (num1, num2); break;
      case '/' : result = Divide   (num1, num2); break;
      default : cout << "Sorry, this is a BASIC calculator ;)\n";
    }
    cout << '\n' << result << "\n";
    cout << "Type any key and ENTER to contunue or Q ENTER to quit ...:";
    cin >> controller;
    system("clear");
  } while(controller != 'Q');
  cout << "Thanks for using my basic calculator !! \n Goodbye :D\n";
  return 0;
}

Please let me know if there is anything I can do to improve this. Now onto arrays / pointers :D

[Juan_8]

Hi it looks good I'm a bigginer in programming and I need to make a simple calculator with an interface. how can I put this code with an interface in Visual C++ 2008 Express and display the result in a dilog box.
Thank you