Is this a proper way of setting up header file?

Question

I'm trying to use classes. And as i go also all the global variables and such. That works out. But how do I implement stuff like #define value 100; in the header?

#ifndef COUNT_H_
#define COUNT_H_

// Definitions
#define first 100;
#define second 200;

// Class definition
class Account {
    private:
    int difficult(int);

    public:
    int easy (int);
} ;

#endif /* COUNT_H_ */

Is this a proper way of doing things? It works, but is it also common?

Don't put semicolons at the end of your defines. Better, don't use `#define`, use proper, typed constants. — Mat, May 18 '14 at 15:55
if you want to use `macros` in expressions, consider using braces `()` around them when defining. If not mandatory, avoid macros and use `const` variables and inline methods. [learn more](http://www.brainbell.com/tutors/c/Advice_and_Warnings_for_C/Macros_and_Miscellaneous_Pitfalls.html) — Rakib, May 18 '14 at 16:00
Also, it might be a good idea to not use #ifndef COUNT_H_, etc. on the header. You could use `#pragma once`, or both for maximum portability. Have a look at this: http://stackoverflow.com/questions/787533/is-pragma-once-a-safe-include-guard — djikay, May 18 '14 at 16:02

score 1 · Answer 1 · answered May 18 '14 at 16:01

1

It's fine to declare a header file like that. You can also use #pragma once in Visual Studios, but I personally prefer not to.

Also as Mat said, it's better to use constants over macros for types. Since you don't have to worry about accidental redefining them.

answered May 18 '14 at 16:01

Callum

25
1
4

I can see benefits using constants, but then I'll have to rewrite my whole program. That's quite a lot of work since it exits out of 18 c files and 18 headers... Also all is written in functions and not in classes. I'm figuring out what benefit it would have for this specific program. – user2371490 May 18 '14 at 18:15

Netherwire · Answer 2 · 2014-05-18T16:21:05.237

You may use defines such as typed global constants visible anywhere from your code and\or from files that #include this file. Defines are usually used as macros:

#define max(a, b)((a > b) ? a : b)

When the define is used, the preprocessor puts the definition in the place your macros was used:

int i = max(a, b); // translated as int i = (a > b) ? a : b;

Just remember that #define is the preprocessor directive, it is almost the same (of course, except the type definition) as compile-time constants such as:

const int CI = 5;

But it significantly differs from runtime constants:

int foo() { return 451; }
const int CJ = foo()

The reason why you shouldn't put the semicolon in your macros (if it isn't necessary, of course, is that when you do this:

#define first 100;

You've made an assignment "first" is "100;" So this code:

int a = first // <- without semicolon

Will be valid

typing ; was a mistake on my behalve. Came with the haste of typing the OP. Just figuring out now whether to change all my #define's into const for my program (which is about 18 .c and .h files big...) — user2371490, May 18 '14 at 18:17
If your program is working the correct way, you don't have to do it. Just keep it in mind later. — Netherwire, May 18 '14 at 19:22

Is this a proper way of setting up header file?

2 Answers2