Basic calculator program in C++

This program is just for two variables to be added up and display the results, but when I run it and input 2 and 2, it gives me 3.21412e-039.

Code:

---

#include <iostream>

using namespace std;

float calc(float a, float b, float c) {
     
      c = a + b;
      cin.get();
      return c;
}

int main() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      calc(a, b, c);
      cout << a << " plus " << b << " equals " << c << " .\n";
      cin.get();
}

---

Why are you passing c as an argument? You should define calc in terms of two arguments and then use c = calc(a, b);

The variable c in the calc function is local to that function, which means that the line c = a + b; does not affect the value of c in main.

Well, I changed it around, but 2+2 seems to equal 1.#QNAN. Sorry, I'm kinda new at this...

Code:

---

#include <iostream>

using namespace std;

float calc(float a, float b) {
    a + b;
    cin.get();
}

int main() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = calc(a, b);
      cout << a << " plus " << b << " equals " << c << " .\n";
      cin.get();
}

---

You still need to declare and return 'c' in your function, not outside, and it need not be passed as a parameter. The code you have really should not compile, as you state that your function retruns a float, but you do not return anything.

Alternatively, you could simply change your function to return the result of addition without the temporary, with 'return a + b;' or, equivalently, 'return (a + b);'.

Well.. that worked. Thanks. And what exactly would be the proper place to put a cin.get(); in a program? I place it at the very end of main(), but it doesn't work.

Most likely because there is a leftover newline character from the previous call to cin::operator>>.

Try adding:
cin.ignore(numeric_limits<streamsize>::max());
Right before your cin.get.

Also, be sure to include <limits> for numeric_limits.

Cheers

Uhhh... I'm like only a day into C++ programming... that code line looks way above my level..

Basically, there could be extra garbage that you don't want in the input buffer. Calling cin.ignore gets rid of that garbage (up to the maximum amount of characters in a stream), so that your cin.get() won't pick up any garbage.

Why do you need cin.get();? Just open a command line and run your program from the command line. That's how command line programs like being run.

No reason not to run the program how you want to. Running from the command line does simplify matters.

Perhaps there is a setting in Windows that prevents terminated "terminals" from closing (I know there is on Mac OS X), but I do not know of it.

Good point. :P

OK, I'm within the Command Prompt thingy, in the folder where my program is, and when I type calc.cpp and press enter, it acts as if it was run through Dev-C++ without a cin.get(). Hmmmm.

EDIT: Scratch that, when I type calc.cpp, it opens it up in Dev-C++ for editing. Poo.

Compile. Type: calc.exe

Yet again, I forget everything I knew while learning basic Java. :P Thanks again...

Also, I don't think i really understand what pointers could be used for. Why not just use the original variables themselves instead of the pointer?

Its because using pointers you can modify the original variable from directly within a function instead of copying the variables over, then manipulating the data and finally returning the data back to main. You have to bear in mind that in your code above, when you pass the variables in, the a and b in your calc function are actually copies of the a and b in your main so in effect, you actually have four variables in memory rather than the two that you expect to have. To modify the original variables from within a function, you either have to use global variables (which should be avoided unless absolutely necessary) or you can use pointers.

I just quickly threw together some code to clarify the above so you can see what I mean:

Code:

---

#include <iostream>

using namespace std;

void calc(int a, int b) {
    a = 10;
    b = 20;
    cout << "Within the calc function a now equals " << a << " and b now equals " << b << "\n";
}

int main()
{
    int a = 2;
    int b = 4;
       
    cout << "Before the calc function a equals " << a << " and b equals " << b << "\n";
    calc(a, b);
    cout << "\nAfter the calc function (back in main) a still equals " << a << "\n";
    cout << "and b still equals " << b << "\n"; 
    cin.get();
    return 0;
}

---

Aaaaaah, I see. Maybe I should implement a pointer into my calculator... not that it would affect the output much, but since I'm a newbie at C++, it's good to experiment.

There is no real need to add a pointer in this context. In particular, it is not a particularly good design choice, in my opinion. There is no reason not to simply return the value.

Going back to your original question for a moment, before you start playing around with pointers:

However, when dealing with parameters, remember that they are copies of the data you send to them, and hence, the variables themselves are local to the function. Even pointers and references are copies (understanding this is an important point).

For example:

Code:

---

#include <iostream>

void foo(int* x)
{
  int a;
  x = &a;
  *x = 5;
}

void bar(int* x)
{
  *x = 5;
}

int main()
{
  int y = 1;
  std::cout << y <<std::endl;
  foo(&y);
  std::cout << y <<std::endl;
  bar(&y);
  std::cout << y <<std::endl;
}

---

Notice that when you change the value of x, you are changing what the temporary (pointer) variable is assigned to (changing what address it points at), so there is no effect on the passed parameter. However, assuming you leave x pointing to the same address passed to the function, it will change your variable, but you are passing an address-of-an-int (which is a value), not an int.

References work the same way in principle, but they have special syntax to make them a bit more transparent. You cannot reassign what a reference points to, and after its initializations, assigning anything to it is really making an assignment to the space in memory that it points to (as I said, special syntax). A consequence of this is, if it would ever be valid to pass a NULL argument, use a pointer... always. In general, it is good practice to prefer passing references when possible as it will make shooting yourself in the foot harder.

As a little example, if you wanted to reassign a pointer (e.g. what foo looks like it does, but doesn't), then you can pass (for example) a reference to a pointer (you could, of course pass a pointer to a pointer... though follow the same guidelines outlined above):

Code:

---

#include <iostream>

void foo(int*& ptr)
{
  ptr = new int;
  *ptr = 7;
}

int main()
{
  int* p = 0;
  foo(p);
  if(!foo)
      std::cout << "Hmm... something is amiss here..." << std::endl;
  else
      std::cout << "*p = " << *p << std::endl;
}

---

Cheers

Ok, I'm kind of stumped again as to what the compiler's complaining about. Here's the fuction with the problem, the compiler errors are "'plus' undeclared (first use this function)" and "'minus' undeclared (first use this function)".

Code:

---

int calc() {
    string cal;
   
    cout << "Do you want to add, subtract, multiply, or divide?\n";
    cin >> cal;
    if (cal == "add") {
            plus();
    }
    else if (cal == "Add") {
        plus();
    }
    else if (cal == "subtract") {
        minus();
    }
    else if (cal == "Subtract") {
        minus();
    }
    else if (cal == "multiply") {
        multi();
    }
    else if (cal == "Multiply") {
        multi();
    }
    else if (cal == "divide") {
        divi();
    }
    else if (cal == "Divide") {
        divi();
    }
}

---

Make sure plus and minus are defined before this function.

Plus() and minus() are the first two defined. Here, I'll post my whole code...

Code:

---

#include <iostream>

using namespace std;

int plus() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a + b;
      cout << a << " plus " << b << " equals " << c << ".";
      cin.ignore();
      cin.get();
}

int minus() {
      float a;
      float b;
      float c;
     
      cout << "Input the number you want to subtract from: ";
      cin >> a;
      cout << "Input the amout you with to subtract: ";
      cin >> b;
      c = a - b;
      cout << a << " minus " << b << " equals " << c << ".";
      cin.ignore();
      cin.get();
}

int multi() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a * b;
      cout << a << " times " << b << " equals " << c << ".";
      cin.ignore();
      cin.get();
}

int divi() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a / b;
      cout << a << " divided by " << b << " equals " << c << ".";
      cin.ignore();
      cin.get();
}

int calc() {
    string cal;
   
    cout << "Do you want to add, subtract, multiply, or divide?\n";
    cin >> cal;
    if (cal == "add" || cal == "Add") {
        plus();
    }
    else if (cal == "subtract" || cal == "subtract") {
        minus();
    }
    else if (cal == "multiply" || cal == "Multiply") {
        multi();
    }
    else if (cal == "divide" || "Divide") {
        divi();
    }
}

void again() {
    string d;
   
    cin >> d;
    if (d == "Y" || d == "y") {
            calc();
    }
    else {
    }
}

int main() {
    string a;

    cout << "Do you wish to use the Calculator? Y/N: ";
    cin >> a;
    if (a == "Y" || a == "y") {
          calc();
          cout << "Would you like to use the calculator again? Y/N: ";
          cin >> a;
          while (a == "Y" || a == "y") {
                again();
                cout << "Would you like to use the calculator again? Y/N: ";
                cin >> a;
          }
    else {
        cin.ignore();
    }
}

---

I don't immediately see why you are having trouble with plus() and minus(), but I do notice that although you say that those first four functions return an int, you have no return statements in them, and the return values (if there were any) are never used. They should have a 'void' return type.

Quote:

---

Make sure plus and minus are defined before this function.

---

They needn't be defined before, just declared (although a definition is more than sufficient).

Code:

---

void foo( ); // <--- declaration

void foo( )
{
} // <--- definition

---

Well, the error seems to be in the calc() function, from what the compiler is telling me. Something about the lines "plus();" and "minus();" are bugging it, but what's odd is that multi() and divi() are fine. I copied and pasted all four from the original plus(), modifying it to fit what they're supposed to do, but you'd think that if I copied and pasted all of them, they'd all have the problem...

Code:

---

#include <iostream>

using namespace std;

void plus() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a + b;
      cout << a << " plus " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void minus() {
      float a;
      float b;
      float c;
     
      cout << "Input the number you want to subtract from: ";
      cin >> a;
      cout << "Input the amout you with to subtract: ";
      cin >> b;
      c = a - b;
      cout << a << " minus " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void multi() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a * b;
      cout << a << " times " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void divi() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a / b;
      cout << a << " divided by " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void calc() {
    string cal;
   
    cout << "Do you want to add, subtract, multiply, or divide?\n";
    cin.ignore(80,'\n');
    cin >> cal;
    if (cal == "add" || cal == "Add") {
        plus();
    }
    else if (cal == "subtract" || cal == "subtract") {
        minus();
    }
    else if (cal == "multiply" || cal == "Multiply") {
        multi();
    }
    else if (cal == "divide" || "Divide") {
        divi();
    }
}

void again() {
    string d;
   
    cin >> d;
    if (d == "Y" || d == "y") {
            calc();
    }
    else {
    }
}

int main() {
    string a;

    cout << "Do you wish to use the Calculator? Y/N: ";
    cin >> a;
    if (a == "Y" || a == "y") {
          calc();
          cout << "Would you like to use the calculator again? Y/N: ";
          cin >> a;
          while (a == "Y" || a == "y") {
                again();
                cout << "Would you like to use the calculator again? Y/N: ";
                cin >> a;
          }
    else {
        cin.ignore(80,'\n');
    }
    return 0;
}

---

Usually compilers just give warnings on no returns maybe you have an option set that makes all warnings errors... try this code. I have also added 80,'\n' to the cin.ignore()'s. That will allow you to enter up to 80 chars or untill you press enter.

No, that still gives the same errors... and warnings are still warnings by my settinngs.

Broke out the compiler... this compiles for me. You had an if{ with no '}' and a couple other errors.

Code:

---

#include <iostream>
#include <string>
using namespace std;

void plus() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a + b;
      cout << a << " plus " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void minus() {
      float a;
      float b;
      float c;
     
      cout << "Input the number you want to subtract from: ";
      cin >> a;
      cout << "Input the amout you with to subtract: ";
      cin >> b;
      c = a - b;
      cout << a << " minus " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void multi() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a * b;
      cout << a << " times " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void divi() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a / b;
      cout << a << " divided by " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void calc() {
    string cal;
   
    cout << "Do you want to add, subtract, multiply, or divide?\n";
    cin.ignore(80,'\n');
    cin >> cal;
    if (cal == "add" || cal == "Add") {
        plus();
    }
    else if (cal == "subtract" || cal == "subtract") {
        minus();
    }
    else if (cal == "multiply" || cal == "Multiply") {
        multi();
    }
    else if (cal == "divide" || "Divide") {
        divi();
    }
}

void again() {
    string d;
   
    cin >> d;
    if (d == "Y" || d == "y") {
            calc();
    }
    else {
    }
}

int main()
{
    string a;

    cout << "Do you wish to use the Calculator? Y/N: ";
    cin >> a;
    if (a == "Y" || a == "y")
        {
          calc();
          cout << "Would you like to use the calculator again? Y/N: ";
          cin >> a;
          while (a == "Y" || a == "y")
                  {
                again();
                cout << "Would you like to use the calculator again? Y/N: ";
                cin >> a;
                  }
        }
    else
        {
        cin.ignore(80,'\n');
    }
    return 0;
}

---

What's the <string> header file do?

Lets you use string.... which is what you are doing... it does alot more than that too lets you compare etc add.

I thought you were able to use the string type without that header file? And I still have the same exact errors.

I got no errors.... and I needed to include it to get rid of the errors about the comparisons and such... no idea why it won't work for you I am using Microsoft's compiler 7.1 maybe that has something to do with it post your errors?

I'm using Bloodshed Dev-C++ as an IDE / compiler-linker. The errors, exactly as the compile shows them, are...

In function `void calc()':
`plus' undeclared (first use this function)
`minus' undeclared (first use this function)

I'm stumped. :(

Hmmmmm someone who has used bloodshed should take over from here lol... I'm not familiar with it in the least. It sounds compiler specific... maybe try making prototypes and then placing all the definitions at the bottom of the code?

Like this:

Code:

---

#include <iostream>
#include <string>
using namespace std;
void fu();
void bar();
int main()
{
  //do stuff
  return 0;
}
void fu()
{
  //do fu's stuff
}
void bar()
{
  //do bar's stuff
}

---

Now it tells me "void '<insert one of the four math functions>()' used prior to declaration". So that didn't work.

Lets see your code as it is now....

Who knew writing a calculator program could be so tough? :P

Code:

---

#include <iostream>
#include <string>

using namespace std;

void plus();
void minus();
void multi();
void divi();

void calc() {
    string cal;
   
    cout << "Do you want to add, subtract, multiply, or divide?\n";
    cin.ignore(80,'\n');
    cin >> cal;
    if (cal == "add" || "Add") {
        plus();
    }
    else if (cal == "subtract" || "subtract") {
        minus();
    }
    else if (cal == "multiply" || "Multiply") {
        multi();
    }
    else if (cal == "divide" || "Divide") {
        divi();
    }
}

void again() {
    string d;
   
    cin >> d;
    if (d == "Y" || "y") {
            calc();
    }
    else {
    }
}

int main()
{
    string a;

    cout << "Do you wish to use the Calculator? Y/N: ";
    cin >> a;
    if (a == "Y" || "y")
        {
          calc();
          cout << "Would you like to use the calculator again? Y/N: ";
          cin >> a;
          while (a == "Y" || "y")
                  {
                again();
                cout << "Would you like to use the calculator again? Y/N: ";
                cin >> a;
                  }
        }
    else
        {
        cin.ignore(80,'\n');
    }
    return 0;
}

void plus() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a + b;
      cout << a << " plus " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void minus() {
      float a;
      float b;
      float c;
     
      cout << "Input the number you want to subtract from: ";
      cin >> a;
      cout << "Input the amout you with to subtract: ";
      cin >> b;
      c = a - b;
      cout << a << " minus " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void multi() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a * b;
      cout << a << " times " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

void divi() {
      float a;
      float b;
      float c;
     
      cout << "Input a number: ";
      cin >> a;
      cout << "Input a second number: ";
      cin >> b;
      c = a / b;
      cout << a << " divided by " << b << " equals " << c << ".";
      cin.ignore(80,'\n');
      cin.get();
}

---

calc and again need to have prototypes too... not just a couple functions.

Still the same errors.

I dont know what to tell you... my code I posted worked on MSVC++ ... and ran just fine except for having to enter y twice in a couple places...

I noticed that bug earlier too. =\

EDIT: Fixed that, it had to do with calling cin twice accedentally.

Ok, I had the bright idea of assimilating plus() and minus() into multi() and divi(). That is, I now have two functions instead of four: multiplus() and diviminus(). Works just fine now. (will edit later if and when I run up another wall)

Ok, I found the next wall. Now, if I input any of my options (add, subtract, multiply, divide), it goes off on this weird loop. First it runs the multiplication part of multiplus(), then the division part of diviminus(), then multiplies again, then divides again, and at the output of the division it prints "I'm sorry, please try again" and "Do you want to add, subtract, multiply, or divide?" all on the same line, looping the entire bug. Also, whether I input Y or N at the very start, it runs the program.


Say nothing about the layout of the code, or what I could do better. I just want to get the bugs fixed first.

Code:

---

#include <iostream>
#include <string>

using namespace std;

void plus();
void minus();
void multi();
void divi();
void calc();

int main()
{
    string a;

    cout << "Do you wish to use the Calculator? Y/N: ";
    cin >> a;
    if (a == "Y" || "Y") {
          while (a == "Y" || "y")
          {
                calc();
                cout << "Would you like to use the calculator again? Y/N: ";
                cin >> a;
          }
    }
    else if (a == "N" || "n") {
        cin.ignore(80,'\n');
        return 0;
    }
}

void multiplus(string cal) {
      float a;
      float b;
      float c;
     
      if (cal == "multiply" || "Multiply") {
              cout << "Input a number: ";
              cin >> a;
              cout << "Input a second number: ";
              cin >> b;
              c = a * b;
              cout << a << " times " << b << " equals " << c << ".";
              cin.ignore(80,'\n');
              cin.get();
      }
      else if (cal == "add" || "Add") {
            cout << "Input a number: ";
            cin >> a;
            cout << "Input a second number: ";
            cin >> b;
            c = a + b;
            cout << a << " plus " << b << " equals " << c << ".";
            cin.ignore(80,'\n');
            cin.get();
      }
      else {
      }
}

void diviminus(string cal) {
      float a;
      float b;
      float c;
     
      if (cal == "divide" || "Divide") {
              cout << "Input a number: ";
              cin >> a;
              cout << "Input a second number: ";
              cin >> b;
              c = a / b;
              cout << a << " divided by " << b << " equals " << c << ".";
              cin.get();
      }
      else if (cal == "subtract" || "Subtract") {
            cout << "Input the number you want to subtract from: ";
            cin >> a;
            cout << "Input the amout you with to subtract: ";
            cin >> b;
            c = a - b;
            cout << a << " minus " << b << " equals " << c << ".";
            cin.ignore(80,'\n');
            cin.get();
      }
      else {
      }
}

void calc() {
    string cal;
    int cas;
   
    cout << "Do you want to add, subtract, multiply, or divide?\n";
    cin.ignore(80,'\n');
    cin >> cal;
    if (cal == "add" || "Add") {
            cas = 1;
    }
    else if (cal == "subtract" || "Subtract") {
        cas = 2;
    }
    else if (cal == "multiply" || "Multiply") {
        cas = 3;
    }
    else if (cal == "divide" || "Divide") {
        cas = 4;
    }
    else {
    }
    switch (cas) {
          case 1:
                multiplus(cal);
          case 2:
                diviminus(cal);
          case 3:
                multiplus(cal);
          case 4:
                diviminus(cal);
          default:
                  cout << "I'm sorry, please try again.";
                  calc();
    }
}

---

I see one problem you didn't prototype your new functions.... In fact all the old prototypes are still there even though the functions aren't. I'll toss that code in my compiler and see what needs to be fixed.

In you main you are using

Code:

---

if (a == "Y" || "Y")

---

this is always true because "Y" is a non zero number when converted to an int which when converted to bool is true( x != 0 is always true) and I believe you wanted "y" there and not "Y".

In fact I think that is your main problem you forgot to put a == or cal == in most if not all of your if statements. That should help you some. When all else fails step through your program with the debugger it is useful.

DOH!! :P I completely forgot! That's definitly a downside of prototypes... And I fixed an error in my main() function's "if" arguments, it had "Y" || "Y" instead of "Y" || "y". Wandering through this mess, fixing some minor bugs...

EDIT: Still the same major bug, though. :(

You need to make it

Code:

---

if(a == "Y" || a == "y")

---

I don't really know how to use Dev-C++'s debugger... :( Otherwise I'll fix those if statements. Oops.

The "Y" || "y" worked fine when I had only the plus() function.

Here is what I came up with this might help yea some.

Code:

---

#include <iostream>
#include <string>
using namespace std;


void diviminus(string );
void multiplus(string );
void calc();

int main()
{
    string a;

    cout << "Do you wish to use the Calculator? Y/N: ";
    cin >> a;
    if (a == "Y" || a == "y")
        {
          while (a == "Y" ||a == "y")
          {
                calc();
                cout << "Would you like to use the calculator again? Y/N: ";
                cin >> a;
          }
    }
    else
        {
        cin.ignore(80,'\n');
        return 0;
    }
}

void multiplus(string cal)
{
      float a;
      float b;
      float c;
     
      if (cal == "multiply" || cal == "Multiply")
          {
          cout << "Input a number: ";
          cin >> a;
          cout << "Input a second number: ";
          cin >> b;
          c = a * b;
          cout << a << " times " << b << " equals " << c << ".";
          cin.ignore(80,'\n');
          cin.get();
      }
      else if (cal == "add" || cal == "Add")
          {
          cout << "Input a number: ";
          cin >> a;
          cout << "Input a second number: ";
          cin >> b;
          c = a + b;
          cout << a << " plus " << b << " equals " << c << ".";
          cin.ignore(80,'\n');
          cin.get();
      }
}

void diviminus(string cal) {
      float a;
      float b;
      float c;
     
      if (cal == "divide" || cal == "Divide") {
              cout << "Input a number: ";
              cin >> a;
              cout << "Input a second number: ";
              cin >> b;
              c = a / b;
              cout << a << " divided by " << b << " equals " << c << ".";
              cin.get();
      }
      else if (cal == "subtract" || cal == "Subtract") {
            cout << "Input the number you want to subtract from: ";
            cin >> a;
            cout << "Input the amout you with to subtract: ";
            cin >> b;
            c = a - b;
            cout << a << " minus " << b << " equals " << c << ".";
            cin.ignore(80,'\n');
            cin.get();
      }
}

void calc()
{
    string cal;
    int cas;
   
    cout << "Do you want to add, subtract, multiply, or divide?\n";
    cin.ignore(80,'\n');
    cin >> cal;
    if (cal == "add" || cal ==  "Add")
        {
        multiplus(cal);
    }
    else if (cal == "subtract" || cal ==  "Subtract")
        {
        diviminus(cal);
    }
    else if (cal == "multiply" || cal ==  "Multiply")
        {
        multiplus(cal);
    }
    else if (cal == "divide" || cal == "Divide")
        {
        diviminus(cal);
    }
        else
        {
          cout << "I'm sorry, please try again.";
          calc();
    }
}

---

Thanks, I'll compare that code to mine in a sec. Turns out you're right about needing cal == "Y" || cal == "Y", as it fixed the "only goes to multi" problem. It still has that wonky bug, exept this time it just repeats the selected function twice, then displays "I'm sorry, please try again" and "Do you want to add, subtract, multiply, or divide?"

Code works perfectly now, thanks! :D Now how would you suggest I make it so you can add as many numbers as you want into the calculations? Like you could input

4 5 7 2 10

and it would output the sum of 4 plus 5 plus 7 plus 2 plus 10, and yet could input

8 1 3 10 2 6 8

without messing up the innards of the code?

Well if you were going to do that would all the numbers be input at the same time or would your output looks somethng like:

Code:

---

Do you want to add, subtract, multiply, or divide?
add
Input a number: 5
Input a number: 6
5 plus 6 equals 11
do you want to add another number? Y
Input a number: 7
11 plus 7 equals 18
do you want to add another number? N

---

Or what kind of formating do you want?

Preferrably your code-box'ed example, since it's more user friendly (or so I personally think).

It wouldn't be much of a code change... you would use recursive calls to do that.... do you need an example?

I'm not too used to using recursive calls, but now that I think of it, I could just use 3 floats and a while loop. :P

Yea you can use a while loop :P was thinking a bit differently and in this case a while would be more efficent I think... Here is an example for a recursive call in case you want to play with it some:

Code:

---

#include <iostream>
#include <string>
using namespace std;

void recursivefunction(int );

int main()
{
  recursivefunction(x);
}


void recursivefunction(int x)
{
  int y;
  string a;
  cout<<"Enter a number: ";
  cin>>y;
  cout<<x<<" plus "<<y<<" equals "<<x+y;
  cout<<"Do you want to add another number? ";
  cin>>a;
  if(a == "y" || a == "Y")
  {
      recursivefunction(x+y);
  }
}

---

Ahh, I see. But don't recursives have a limit on how many times they can recurse? I don't know how many, since I didn't test the recurse example in the recursion part of the tutorial here, though.

I just added this block of code onto the end of each half of the two math functions, and it works! :D

Code:

---

            cout << "Would you like to add in another number? Y/N\n";
            cin >> yn;
            while (yn == "Y" || yn == "y") {
                  cout << "Input a number: ";
                  cin >> b;
                  c += b;
                  cout << "Your new total is " << c << ".\n";
                  cout << "Would you like to add in another number? Y/N\n";
                  cin >> yn;
            }

---

I'm trying to add support for modulus into the calculator, but what exactly is the operator for it? I'm using the statement c = a % b; for the main part of the function, and c %= b; for the while loop.

The limit of a recursive function is the amount of RAM in the computer since each call takes a little bit more data... modulus is used with the syntax

Code:

---

a = b%c;

---

it will give you the remander if b was divided by c.

It is also used in generating random numbers as an example:

Code:

---

.
.
.
int randomnumber;
srand(clock());
randomnumber = 1+rand()%100;    //this is a number between 1 and 100
randomnumber = 25+rand()%76;    //this is a number between 25 and 100
.
.
.

---

On the uses of modulus, neat. On the syntax of it, you mean I would use it as "c = a%b" and "c %=b" instead? Or am I wrong? :(

Code:

---

c %= b;

---

this is equivalent to the statement:
If it even compiles I have never used it like that...

Code:

---

c = c%b;

---

Well, it doesn't compile, hehe. Even the x = x%x version doesn't compile, though. It tells me "invalid operands of types "float" and "float" to binary "operator%"". Is there any special header file I need?

you need to do this then

c = (int)x%(int)y; //cast the other two vars as ints mod won't work for floats

K, it works now. Just need to allow the user to access the function in the first place. Unfortunately, it's giving me an "undeclared" error. *yawn*

EDIT: Hah, its reason for being undeclared was that modulus isn't a legal function name (or so my observations tell me). With my previous plus() and minus() functions, it was probably the same problem! :D

O yea you cant do that lol... Use things like MyModulus :P

I'm just calling it mod(). I'm just gonna assimilate mod() into the division half of diviminus() so that it outputs both the result of division and the remainder, and then I'll be pretty much done with the calculator.

Sounds good to me. I noticed you fixed the double entrys at some point. Forgot to mention that.

Double entries? *confused*

A while back you had to enter y twice to get into the function :P guess it was longer ago than I thought lol.

Oh, yeah. I mentioned that earlier, and said it had to do wit haccedentally calling "cin" twice.

Speaking of bugs, I have a minor but weird one on in the text-based game I'm writing. It's on another topic if you want to take a look.

Quote:

---

you need to do this then

c = (int)x%(int)y;

---

That will result in loss of precision. If you don't want that, include <math.h> and use the fmod() function. It takes two double [floating-point] arguments and moduluses them.

Code:

---

#include <math.h>

printf("%lf", fmod(10.0, 8.2));

---

You mean <cmath> and cout, right? THis is the C++ part of the board. Thanks, though. ^_^ (if you can't tell, ^_^ is a smiley).

EDIT: Hey, that works pretty well! I just implemented it. :D

Sorry, and you're welcome. :)