Hi,
I have two different enum definitions with members of same name. The
compiler complains about duplicate definitions. Is this expected
behaviour?
Can't I have same-named fields in different enum definitions? I think
it should have been perfectly valid to do that. Its a stupid limitation
to have to define disjoint enum symbol definitions. This is like having
to have disjoint member names in structures.
Bahadir
21  6352 
On 2 Jun 2005 09:12:04 -0700, Bi************* @gmail.com wrote: Hi,
I have two different enum definitions with members of same name. The
compiler complains about duplicate definitions. Is this expected
behaviour?
Yes, enumeration constants are in one and the same namespace (which
they share with functions, variables and typedef names).
See 1.29 from the FAQ. Bi************* @gmail.com wrote:
Hi,
I have two different enum definitions with members of same name. The
compiler complains about duplicate definitions. Is this expected
behaviour?
Can't I have same-named fields in different enum definitions? I think
it should have been perfectly valid to do that.
Its a stupid limitation
to have to define disjoint enum symbol definitions.
This is like having
to have disjoint member names in structures.
Not really. You have no way of knowing which enum
a member belongs to, if members have the same name.
enum forward {ZERO, ONE};
enum backward{ONE, ZERO};
return ZERO;
Perhaps,
if your enum members have the same name at the same value,
you could do better with only one enum?
--
pete Bi************* @gmail.com writes: I have two different enum definitions with members of same name. The
compiler complains about duplicate definitions. Is this expected
behaviour?
Yes.
Can't I have same-named fields in different enum definitions?
No.
I think it should have been perfectly valid to do that. Its a
stupid limitation to have to define disjoint enum symbol
definitions. This is like having to have disjoint member names
in structures.
You could always switch to C++. It has features that can do what
you want. Short of that, the standard practice is to use a
unique prefix for each enumerated type.
--
Ben Pfaff
email: bl*@cs.stanford .edu
web: http://benpfaff.org Bi************* @gmail.com wrote: Hi,
I have two different enum definitions with members of same name. The
compiler complains about duplicate definitions. Is this expected
behaviour?
Can't I have same-named fields in different enum definitions? I think
it should have been perfectly valid to do that. Its a stupid limitation
to have to define disjoint enum symbol definitions. This is like having
to have disjoint member names in structures.
Bahadir
Enumeration constants in C are of type `int' and enumeration constant
identifiers are unqualified when used. If the same identifier occurs in
different enumerations there is no way for the compiler to know which
one to use.
-- August
August Karlstrom wrote: Bi************* @gmail.com wrote:
Hi,
I have two different enum definitions with members of same name. The
compiler complains about duplicate definitions. Is this expected
behaviour?
Can't I have same-named fields in different enum definitions? I think
it should have been perfectly valid to do that. Its a stupid limitation
to have to define disjoint enum symbol definitions. This is like having
to have disjoint member names in structures.
Bahadir
Enumeration constants in C are of type `int' and enumeration constant
identifiers are unqualified when used. If the same identifier occurs in
different enumerations there is no way for the compiler to know which
one to use.
Which brings us to the question why enumerations in C aren't qualified.
Probably because that way things would get rather verbose:
f(SomeEnum.A_CO NSTANT | SomeEnum.ANOTHE R_CONSTANT
| SomeEnum.A_THIR D_CONSTANT);
rather than
f(A_CONSTANT | ANOTHER_CONSTAN T | A_THIRD_CONSTAN T);
-- August Bi************* @gmail.com wrote: Hi,
I have two different enum definitions with members of same name. The
compiler complains about duplicate definitions. Is this expected
behaviour?
Can't I have same-named fields in different enum definitions? I think
it should have been perfectly valid to do that. Its a stupid limitation
to have to define disjoint enum symbol definitions. This is like having
to have disjoint member names in structures.
Another strategy is to forget the `enum' feature and use plain integer
constants (I use double quotes for these pseudo enumerations from now
on). As long as all "enumeratio n" constants have distinct values, there
is no problem with sharing a constant between different "enumeratio ns".
This is also a safer approach since if a client uses an "enumeratio n"
constant from the wrong "enumeratio n" it will be detected.
-- August
August Karlstrom <fu********@com hem.se> writes:
[...] Which brings us to the question why enumerations in C aren't
qualified. Probably because that way things would get rather verbose:
f(SomeEnum.A_CO NSTANT | SomeEnum.ANOTHE R_CONSTANT
| SomeEnum.A_THIR D_CONSTANT);
rather than
f(A_CONSTANT | ANOTHER_CONSTAN T | A_THIRD_CONSTAN T);
The language *could* have been defined so that an enumeration constant
can be used without qualification if there's no ambiguity, with some
kind of qualification syntax to be used if there's another constant of
the same name. There are languages that do this. C, unsurprisingly,
isn't one of them.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.
Keith Thompson wrote: August Karlstrom <fu********@com hem.se> writes:
[...]
Which brings us to the question why enumerations in C aren't
qualified. Probably because that way things would get rather verbose:
f(SomeEnum.A_CO NSTANT | SomeEnum.ANOTHE R_CONSTANT
| SomeEnum.A_THIR D_CONSTANT);
rather than
f(A_CONSTANT | ANOTHER_CONSTAN T | A_THIRD_CONSTAN T);
The language *could* have been defined so that an enumeration constant
can be used without qualification if there's no ambiguity, with some
kind of qualification syntax to be used if there's another constant of
the same name. There are languages that do this. C, unsurprisingly,
isn't one of them.
What language do you have in mind?
August Karlstrom <fu********@com hem.se> writes: Keith Thompson wrote: August Karlstrom <fu********@com hem.se> writes:
[...]
Which brings us to the question why enumerations in C aren't
qualified. Probably because that way things would get rather verbose:
f(SomeEnum.A_CO NSTANT | SomeEnum.ANOTHE R_CONSTANT
| SomeEnum.A_THIR D_CONSTANT);
rather than
f(A_CONSTANT | ANOTHER_CONSTAN T | A_THIRD_CONSTAN T);
The language *could* have been defined so that an enumeration
constant
can be used without qualification if there's no ambiguity, with some
kind of qualification syntax to be used if there's another constant of
the same name. There are languages that do this. C, unsurprisingly,
isn't one of them.
What language do you have in mind?
<OT>
Ada.
Given a type declaration
type Enum is (Zero, One, Two);
each constant is equivalent to a function with no parameters returning
Enum. (Ada doesn't use empty parentheses for parameterless function
calls.) Enumeration constants aren't really implemented as functions,
and they can be used in constant expressions, but it allows all the
overloading rules that apply to functions to apply to enumeration
constants.
</OT>
Using the same approach in C would violate the "Spirit of C", I think.
Using another approach that's specific to enum types (and inventing a
syntax for the qualification) probably wouldn't be worth the effort.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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