Thread: enum values not working in #define?

So yet again I'm working through the teach yourself c++ in 21 days and I am stuck again.

This is in regard to different debugging macro levels.

Heres the example...

Code:

#include <iostream>
#include <string.h>

using namespace std;

enum LEVEL { NONE, LOW, MEDIUM, HIGH };
const int FALSE = 0;
const int TRUE = 1;
typedef int BOOL;

#define DEBUGLEVEL LOW

#if DEBUGLEVEL < LOW
#define ASSERT(x)
#else
#define ASSERT(x) \
    if (! (x)) \
    { \
        cout << "ERROR!! Assert " << #x << " failed\n"; \
        cout << " on line " << __LINE__ << "\n"; \
        cout << " in file " << __FILE__ << "\n"; \
    }
#endif

#if DEBUGLEVEL < MEDIUM
#define EVAL(x)
#else
#define EVAL(x) \
    cout << #x << ":\t" << x << endl;

#endif

#if DEBUGLEVEL < HIGH
#define PRINT(x)
#else
#define PRINT(x) \
     cout << x << endl;
#endif

So depending on what I set DEBUGLEVEL to be should decide what methods I want. As it stands the output always acts as if I'm using HIGH, but if I just use numbers such as...

Code:

#define DEBUGLEVEL 1

#if DEBUGLEVEL < 1

it works as expected.

so whats up with the enum LEVEL stuff not working?

The preprocessor doesn't know anything about the language. For all it knows, HIGH is the same as SNORKEL -- it's just a bunch of letters.

Its copied straight from the book, how do I fix it?

OK so why would the book try to use an enumeration if the preprocessor doesn't understand it?

Originally Posted by MattJ812

OK so why would the book try to use an enumeration if the preprocessor doesn't understand it?

I'm not seeing this example in the book. Do you have a page number?

Hmm. Listing 17.8 in the copy I'm looking at is about cin.ignore(). Granted I can only look at the 5th ed. Perhaps they realized it was an atrocious idea and took it out. The #define part works just fine. But you won't be able to use < and > with it.

OK so you're saying the enumeration works aslong as I don't test if the DEBUGLEVEL is less or greater than? Why is that?

And you say you have the 5th edition? where do I get it? mine is 2nd i didn't download it very long ago.

Were they valid types when they wrote that?

Im sorry I was under the assumption that this book was kept up online, it took long enough to figure out how to get a compiler to even start to learn from it.

My school has a subscription to Safari Online; many libraries do.

#define just does text substitution. Sprinkling the word HIGH throughout your code is just fine, because your enum will turn that into a number. But the preprocessor does not know -- has no way of knowing or caring -- about that value, and as such any attempt to actually use the value is doomed to failure.

I'm not in school I've been wanting to code games forever and learned a whole bunch about GML but I wanted to learn more about "proper" coding and c++ in 21 is what I found so here I am.

Learn as I go I guess, hard to do when your learning materials are wrong heh.

Thanks tho.

Originally Posted by MattJ812

I'm not in school I've been wanting to code games forever and learned a whole bunch about GML but I wanted to learn more about "proper" coding and c++ in 21 is what I found so here I am.

Learn as I go I guess, hard to do when your learning materials are wrong heh.

Thanks tho.

You're going to find that everywhere...

Self-publishing has so thoroughly diluted the wisdom pool that you're actually more likely to get bad information than good, at least the first time around... The real trick is to tell them apart.

A few years back, learning C I must have gone through about 5 books and tutorials looking for one that A) understood I was a beginner and B) wasn't chock full of mistakes. I eventually muddled through and got reasonably good at it. If you read the other threads here you'll see I just went through it again with C++ ... I was blocked on the whole OOP thing; no matter what I did it simply would not sink in. The tutorials and books (including C++ in 21 Days) did little more than deepen the confusion. Asking questions (other than here) more often made it worse than better...

Just a few days ago I pushed the point here and got a flood of extremely helpful discussion and a reference to "Thinking In C++". Between the two it's finally sinking in.... Or, pehaps I should say it "seems to be" sinking in, I've yet to put it to the test.

I think you'll find your best plan is to get a decent tutorial on plain C and work through it to give yourself the fundimentals, do a couple of simple programs, then climb into the "Thinking in C++" books... Although they are two separate languages, there is enough similarity that knowing C helps with C++ ...

Oddly the C in 21 days tutorial is pretty good...
Teach Yourself C in 21 Days -- Table of Contents

Thinking in C++ is here...
Bruce Eckel's MindView, Inc: Thinking in C++ 2nd Edition by Bruce Eckel

All editions will have errata.