Macro question

Code:

#define XXX_A0_YYY "foo"
#define XXX_A1_YYY "bar"
#define getXXX(id) XXX_##id##_YYY

The idea is that getXXX(A0) expands to XXX_A0_YYY and thus the result of "cout << getXXX(0)" is "foo".

However, instead I get the following error message from the compiler: "XXX_id_YYY is undefined".

Why is it not replacing 'id' with the passed parameter?

If I remove "XXX_" from all of the above, it works correctly:

#define A0_YYY "foo"
#define A1_YYY "bar"
#define getXXX(id) id##_YYY

Now "cout << getXXX(A0)" works and prints "foo" on the screen.

Quote:

---

Originally Posted by Mole42

The idea is that getXXX(A0) expands to XXX_A0_YYY and thus the result of "cout << getXXX(0)" is "foo".

---

I think you meant to say that 'the result of "cout << getXXX(A0)" is "foo"'. This works for me:

Code:

---

#include <iostream>

#define XXX_A0_YYY "foo"
#define XXX_A1_YYY "bar"
#define getXXX(id) XXX_##id##_YYY

int main()
{
    using namespace std;
    cout << getXXX(A0) << endl;
}

---

I tried that, I get

"Undefined identifier: XXX_id_YYY"

If I change:

#define getXXX(id) XXX_##id##_YYY

to:

#define getXXX(id) id##_YYY

then I get

"Undefined identifier: A0_YYY"

Which is what I expect.

I'm beginning to think it's a bug in the pre-processor.

You could be right there. What compiler is it?

I would expect that error message if you called it as getXXX(id) instead of getXXX(A0).