Difference between enum and #define preprocessor

[ashwani]

Hi
Can any one tell me the difference between preprocessor macros like
#define and enum.
If i want to define MAX_LIMIT=100 as preprocessor macro as
#define MAX_LIMIT 100
or if i define enum {MAX_LIMIT=100}; then what is the basic difference?
Is there any efficiency tradeoff between both the definitions.

 

[Ivan Vecerina]

: Hi
: Can any one tell me the difference between preprocessor macros like
: #define and enum.
: If i want to define MAX_LIMIT=100 as preprocessor macro as
: #define MAX_LIMIT 100
: or if i define enum {MAX_LIMIT=100}; then what is the basic difference?
: Is there any efficiency tradeoff between both the definitions.

No difference in efficiency.

enum-declared constants are to be preferred because they
obey scoping rules (e.g. they can be encapsulated within
a class or namespace).

In a modern compiler, using
const int MAX_LIMIT = 100;
or
static const int MAX_LIMIT = 100;
is also likely to be just as efficient (no space or time
overhead) as a define.

 

[Rolf Magnus]

Hi
Can any one tell me the difference between preprocessor macros like
#define and enum.
If i want to define MAX_LIMIT=100 as preprocessor macro as
#define MAX_LIMIT 100
or if i define enum {MAX_LIMIT=100}; then what is the basic difference?

enum respects scope, #define doesn't.

Is there any efficiency tradeoff between both the definitions.

no.

Btw: If you want a constant, just define a constant and not a macro or an
enum.

 

[Frederick Gotham]

ashwani posted:

Hi
Can any one tell me the difference between preprocessor macros like
#define and enum.
If i want to define MAX_LIMIT=100 as preprocessor macro as
#define MAX_LIMIT 100
or if i define enum {MAX_LIMIT=100}; then what is the basic difference?
Is there any efficiency tradeoff between both the definitions.

namespace MyNamespace {

#define ONE 1

enum { TWO = 2 };

int const three = 3;
}

int main()
{
ONE; /* No problem */

TWO; /* Can't find it */

three; /* Can't find it */


MyNamespace::ONE; /* Gibberish! */

MyNamespace::TWO; /* No problem */

MyNamespace::three; /* No problem */
}