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p124 K&R

 
 
Barry Schwarz
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      08-06-2008
On Tue, 05 Aug 2008 20:18:52 +0100, Flash Gordon
<(E-Mail Removed)> wrote:

>Barry Schwarz wrote, On 05/08/08 18:23:
>> On Tue, 5 Aug 2008 05:53:57 -0700 (PDT), mdh <(E-Mail Removed)> wrote:
>>
>>> On Aug 3, 10:56 pm, Barry Schwarz <(E-Mail Removed)> wrote:
>>>> On Sun, 3 Aug 2008 19:25:26 -0700 (PDT), mdh <(E-Mail Removed)> wrote:
>>>
>>>
>>>>> On Aug 3, 6:30 pm, Barry Schwarz <(E-Mail Removed)> wrote:
>>>> In order for the enum declaration to define an object, you would have
>>>> to name the object as part of the declaration. Something along the
>>>> lines of
>>>> enum {...} x;
>>>> would define the object (variable) x of the enum type. ....
>>> ...snip...
>>>
>>>
>>>> Your (actually K&R's)
>>>> original enum statement did not define an object and so is in keeping
>>>> with this general rule.
>>> So is it fair to say one can use enums in 2 general ways.
>>>
>>> One...without an (enum) identifier in which case the list identifiers
>>> are used as a substitute for simple #define statements.

>>
>> I think this is true but I don't know if it is complete. What I mean
>> is that the enumerators appear to act the same as simple macro names
>> but I don't know if there are any other aspects. For example, if you
>> view an object of enum type in the debugger, do you see the integer
>> value or the name or the enumerator? With a macro the answer is
>> obviously the integer value but with an enumerator?

>
>That all depends on the debugger. Some debuggers even know about macros
>these days!
>
>Another advantage of using an enum is that the identifiers then follow
>"normal" C scoping unlike macros. Comnsider the following...
>
>int foo() {
>#define BUFSIZ 50
> unsigned char buf[BUFSIZ];
>...
>
>int bar() {
> enum { BUFSIZ=50 };
> unsigned char buf[BUFSIZ];


Thank you. I knew there had to be a non-trivial distinction but I
couldn't think of what it might be.

>...
>
>
>>> Two...with an identifier, in which case one can declare a variable of
>>> type "enum myenum" and assign to that variable one of the list
>>> constants ?
>>>
>>> In either case, if I wish to used that enum in another file ( ?
>>> translation unit) I need to **declare** it either in the header or
>>> before using it in that **other** function.

>>
>> Just like a macro name.

>
>Indeed. Also like a typedef or struct definition.


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