error C2065: undeclared identifier PLEASE HELP!

ok so im trying to learn switch cases so i tried to write this program to see if i understood how to write them and i wrote both my variables the same exact way and its only giving me an undeclared variable for 1 of them. here's my code, please help.

Code:

---

#include <iostream>

using namespace std;

int main ()
{
        int a;
        int b (b = 1);
        int c (c = 2);

        for (a = 0; a < 3; a++) {
                switch (a) {
                        case b:
                                {
                                        cout<< "wow this is really confusing\n";
                                }
                                break;
                        case c:
                                {
                                        cout<< "now it's a little easier\n";
                                }
                                break;
                        default:
                                {
                                        cout<< "X-P\n";
                                }
                                break;
                }
        }
}

---

I think you mean

Code:

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int b(2);

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and similarly for c. Also I don't believe you can use variables in case statements, only constants.

thank you so should that part of the code look like

Code:

---

int a;
int b(1);
int c(2);

---

i tried compiling that and it said "case expression not constant." for both b and c.

whats the difference between variables and constants? sorry im a beginner haha

Variable Definition | Definition of Variable at Dictionary.com

Constant Definition | Definition of Constant at Dictionary.com

ya i know that i meant whats the difference in writing them in c++

A constant is something like 6. Or 11. Or 253. Something that is constant according to the English sense of the term.

yeah so how would i write it because when i write it like this it says "case expression not constant."

Code:

---

int a;
int b(1);
int c(2);

---

Quote:

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Originally Posted by dyelax

yeah so how would i write it because when i write it like this it says "case expression not constant."

---

What are you trying to do?

this is the whole code:

Code:

---

#include <iostream>

using namespace std;

int main ()
{
        int a;
        int b(1);
        int c(2);

        for (a = 0; a < 3; a++) {
                switch (a) {
                        case b:
                                {
                                        cout<< "wow this is really confusing\n";
                                }
                                break;
                        case c:
                                {
                                        cout<< "now it's a little easier\n";
                                }
                                break;
                        default:
                                {
                                        cout<< "X-P\n";
                                }
                                break;
                }
        }
}

---

What your compiler is trying to tell you is that the expression used in a case must be a constant, i.e., you should write:

Code:

---

#include <iostream>

using namespace std;

int main()
{
    for (int a = 0; a < 3; a++) {
        switch (a) {
        case 1:
            {
                cout<< "wow this is really confusing\n";
            }
            break;
        case 2:
            {
                cout<< "now it's a little easier\n";
            }
            break;
        default:
            {
                cout<< "X-P\n";
            }
            break;
        }
    }
}

---

ooooohhhhhh. so the case has to be a number?

thank you! it runs now! I'm sorta confused why you dont have to have "int a;" at the beginning before the loop

You do have to have int a before the loop.(*) And since you have it, everybody's happy.

(*)You are allowed to have it inside the loop itself, as in

Code:

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for (int a = 0; a < 3; ++a)

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all right thank you