Getting the address of an enum constant

[srikar]

hi all
when I am running the below program

#include<iostre am>
enum one
{
a=1000,b=2000,c ,d,z};
int main()
{
one* a1;one* a2;one* a3;
a1=&a;a2=&b;a3= &c;
int fun1(one*,one*, one*);
int x;
cout<<"the starting values are"<<a<<"\t"<< b<<"\t"<<c<<"\t "<<d<<"\t"< <z;
x=fun1(a1,a2,a3 );
cout<<"the sum of the values are\t"<<d;
return 0;}
int fun1(one *a,one *b,one *c)
{
return (*b-*a);
}

I am getting the following errors
non-lvalue in unary `&'
enumptr.cpp:9: non-lvalue in unary `&'

Actually I want to pass the address of the variables a,b,c using the pointers
a1,a2,a3 using the function fun1
I am assigning the adress of a,b,c to a1,a2,a3 using "&" operator
Is it the wright way of assigning the address in C++

please help me

[arne]

Actually I want to pass the address of the variables a,b,c using the pointers
a1,a2,a3 using the function fun1

The problem is that a,b, ... are no variables, but enumeration constants. Try something like

int a = 1000;
int *a1;
a1 = &a;
 

This should work.

[srikar]

The problem is that a,b, ... are no variables, but enumeration constants. Try something like

int a = 1000;
int *a1;
a1 = &a;
 

This should work.

Thanks for the fast reply,
Its working with int format
what about the enum, is it that enum constats cant be stored in pointers

regards
srikar

[arne]

Thanks for the fast reply,
Its working with int format
what about the enum, is it that enum constats cant be stored in pointers

regards
srikar

Enumerations simply asssociate names with integer values. Therfore, names in enumerations are very similar to constants defined using #define. The only two advantages of enums I am aware of are that
- the assignment of the values happens automatically, and
- the names may persist through to the debugger (which may help with debugging).

You can, however, define enumeration variables and access the address of them, but at the moment I have no idea what that may be good for ...

[srikar]

Enumerations simply asssociate names with integer values. Therfore, names in enumerations are very similar to constants defined using #define. The only two advantages of enums I am aware of are that
- the assignment of the values happens automatically, and
- the names may persist through to the debugger (which may help with debugging).

You can, however, define enumeration variables and access the address of them, but at the moment I have no idea what that may be good for ...

Thanks for the information given
So enum values cannot be assigned to pointer variables.
Can we make casting for enum variables to data types other than int.
regards
srikar

[arne]

Thanks for the information given
So enum values cannot be assigned to pointer variables.
Can we make casting for enum variables to data types other than int.
regards
srikar

Enumerators (enumeration constants) are no variables, they're constants. They can be used whenever you use an integral type.

How would such a "cast to data types other than int" look like?

[srikar]

Hi thanks once again.

Can we type cast a enum value with (void*) inorder to get the adress on
a 32 bit machine. Is it possible.

regards
srikar

[srikar]

hi all,
how to get the address of an enum constant.
Can we make type casting of enum constant to (void*) on 32 bit machine where
both enum and address are of same size.
please help me

[arne]

Hi thanks once again.

Can we type cast a enum value with (void*) inorder to get the adress on
a 32 bit machine. Is it possible.

regards
srikar

Sure, you can instantiate an enum (just as a struct or a union):

#include <stdio.h>
 
enum Num { jan, feb, mar };
 
int main( void )
{
    enum Num a;
 
    printf( "%p\n", &a );
 
    return 0;
}
 

But for what could you use that?

[Banfa]

You can't, an enum defined value has no memory space, therefore it has no address.