same value enum

[mikron30]

Hi,

Is it legal to create two enums with the same value?

typedef enum {
a,
b=a,
c
} save_value_enum;

It passed compilation in Visual Studio 6 and gcc 2.95. But I am not
sure if it is ANSI. I didn't find any saying (for or against) in
Stroustrup.

Thanks,
Miki Zilbershtein

 

[joe.els]

Hi

It is legal in the way that you're allowed to assign values to enums.
Example:
enum MyEnum
{
EA = 0,
EB = -1,
EC = 10,
ED = EC
};

However having duplicate values in your enumerations doesn't make any
logical sense. Enumerations are commonly used as unique constants. If
you take away the uniqueness, then enumerations become less useful.

Also using an enumerations with duplicate values in a switch-statement
won't compile.
Example:
switch (/* some value */)
{
case EA:
...
break;
case EB:
...
break;
case EC:
...
break;
case ED:
...
break;
};

Because EC and ED has the same value of 10, the switch-statement would
break the compilation, giving you some message about duplicate values.


Joe