Beginner needs help with If Statement

Hi, i recently developed a desire to learn how to program. After asking around, I was told to pick up C++ as the programing language to learn. I downloaded the free Microsoft Visuall C++ Express and whipped out the cprograming.com tutorial. In the first tutorial it gives you a basic program

Code:

---

#include <iostream>

using namespace std;

int main()
{
  int thisisanumber;

  cout<<"Please enter a number: ";
  cin>> thisisanumber;
  cin.ignore();
  cout<<"You entered: "<< thisisanumber <<"\n";
  cin.get();
}

---

After working this threw a couple times i decided to toy around and wrote a simple program using the base code, but adding an extra line for a second number and then subtracted the two and then gave you an answer. This too worked out fine. After reading the next chapter on If statements, i decided to go back and get more indepth. Setting up a couple different variables and then asking the user to imput what type of math, be it addition subtraction multiplication etc and then execute a series of commands to provide them with a simple answer. So far the code i have writen is such

Code:

---

#include <iostream>

using namespace std;

int main()
{
  int firstnum;
        int secondnum;
        int equals;
        char sub;
        char add;
        char multiply;
        char choice;
       
cout<<"Please choose one:Add Multiply Or Subtract";
        cin>>choice;
        cin.ignore ();
        If (choice == sub); {
          cout<<"Please enter a number: ";
      cin>> firstnum;
      cin.ignore();
      cout<<"please enter a number to subtract: ";
      cin>> secondnum;
      cin.ignore ();
          equals = firstnum - secondnum;
      cout<<"Your answer is: "<< equals <<"\n";
      cin.get(); }
        Else (choice == add) {
                cout<<"Please enter a number:";
                cin>> firstnum;
                cin.ignore();
                cout<<"Please enter a number to add: ";
                cin>> secondnum;
                cin.ignore ():
                equals = firstnum + secondnum;
                cout<<"You answer is:" <<equals <<"/n";
                cin.get(); }
}

---

Since i am new, i stopped after the first two functions and debugged. I keep getting two identical errors when i debug the program. "Error C3861 If identifier not found and Else identifier not found. I tried using the help section of Visual C++ plus provide insight on the error code and it explains how to fix it, in a way that I have not learned yet. So I am hoping somebody out there can spot my mistake and help me correct it.

Thanks.
ps i hope the code tag worked, first time posting.

Ok. Firstly I'm going to say that I appreciate that learning programming is hard. So stick at it!!

Secondly, both C and C++ are both case sensitive, so if isn't the same as If, nor is else the same as Else. It's only the lower case versions which should work (it's likely that they're typedeffec of defined somewhere, but ... )

The best way to do this is to do something like:

Code:

---

char option;
int firstnum, secondnum, answer;

cout<< "Enter your first number: ";
cin >> firstnum;

cout<< "Enter your second number: ";
cin >> secondnum;

cout<< "Do you want to (m)ultiply, (d)ivide, (s)ubtract or (a)dd those two numbers?";
cin >> option;

if ( option == 'm' )
{
  // Do multiplication stuff here
}
else if ( option == 'd' )
{
  // do division stuff here
}
else if ( option == 's' )
{
  // do subtraction
}
else if ( option == 'a' )
{
  // do addition stuff
}
else
{
  cout<< "That option is not available here";
}

---

Now. Look at that for and see if you can see why it doesn't work as you would like

In your code you made characters called add, subtract etc. These aren't initialised in your code (not given initial values), so saying if something == something else will have indefined effects. You could have said:

Code:

---

char add='a';
char subtract = 's';
char multiply = 'm';
char divide = 'd';

---

and then added a

Code:

---

if ( option == add )
{
  [..]
}

---

thing, but there's no need.

You'd probably want these variables to be constant, unless you plan on changing them.

Code:

---

char add='a';
char subtract = 's';
char multiply = 'm';
char divide = 'd';

---

->

Code:

---

const char add='a';
const char subtract = 's';
const char multiply = 'm';
const char divide = 'd';

---

If you're using constant values, it looks like a sure case for a switch statement.

You could always use an array of function pointers. :D

BTW, you could always use '+' instead of 'a' etc.

I changed the uppercase If and Else statements, and the program debugged completely. I ran the program and it Asked the opening statement, Please choose one:(A)dd (M)ultiply Or (S)ubtract:"

After you enter your choice, the window just closes. Not really sure what to do now, since im just starting to learn, i cant really troubleshoot anything without the debugger telling me where an error is, since i dont know what is right and what is wrong.

If anybody wants to take the time to look it over, ill post the whole code. Its not very long

Code:

---

#include <iostream>

using namespace std;

int main()
{
  int firstnum;
        int secondnum;
        int equals;
        int sub =' s ';
        int add = ' a ';
        int multiply = ' m ';
        int choice = ' c ';
       
        cout<<"Please choose one:(A)dd (M)ultiply Or (S)ubtract:";
        cin>>choice;
        cin.ignore ();
        if (choice == sub) {
          cout<<"Please enter a number: ";
      cin>> firstnum;
      cin.ignore();
      cout<<"please enter a number to subtract: ";
      cin>> secondnum;
      cin.ignore ();
          equals = firstnum - secondnum;
      cout<<"Your answer is: "<< equals <<"\n";
      cin.get(); }
        else if (choice == add) {
                cout<<"Please enter a number:";
                cin>> firstnum;
                cin.ignore();
                cout<<"Please enter a number to add: ";
                cin>> secondnum;
                cin.ignore ();
                equals = firstnum + secondnum;
                cout<<"You answer is:" <<equals <<"\n";
                cin.get(); }
        else if (choice == multiply); {
                cout<<"Please enter first number:";
                cin>> firstnum;
                cin.ignore ();
                cout<<"Please enter Second number to Multiply";
                cin>> secondnum;
                cin.ignore ();
                equals = firstnum * secondnum;
                cout<<"Your answer is:" <<equals <<"\n"; }


        }

---

Code:

---

int sub =' s ';

---

Your compiler should give you a warning for that, something about "multicharacter constants". It should be

Code:

---

int sub = 's';

---

or maybe

Code:

---

char sub = 's';

---

or maybe

Code:

---

const char sub = 's';

---

This semicolon really messes up your code. Get rid of it.

Code:

---

else if (choice == multiply); {

---

For code like this,

Code:

---

if(x); {
    // ...
}

---

the compiler sees

Code:

---

if(x) {}

{  /* always executes */
    // ...
}

---

You're writing it much longer than it needs to be. Prompt for the numbers outside the if statements. The user input could look something like this

Code:

---

Enter the operator: +
Enter the first number: 3.14159265359
Enter the second number: 1.0
3.141593 + 1.000000 = 4.141593

---

and your pseudocode

Code:

---

get operator
get number 1
get number 2
if operator is '+'
    result = number1 + number2
else if operator is '-'
    result = number1 - number2
etc

---

I prefer to use enum for declaring such consts, it will group and show all possibilities at once

Code:

---

enum operations
{
  add = 'a',
  sub = 's',
etc
};

---

So anyone wondering what are the possible operations supported - has one place to look for

I particularily like enums for values that increment each time, because the compiler does the calculations for you. You make less mistakes that way.

There are arguments against using what some call the "enum-hack", though. One thread comes to mind: http://cboard.cprogramming.com/showthread.php?t=85992

Basically, you can make constants in three ways (AFAIK).

1. With enums.
2. With constant variables.
3. With #defines.

The third is usually a bad idea in C++, and the first two have been mentioned in this thread.

>With #defines.

Hmm takes me back to the old C language sytle of the mid 90s