Is that a constant expression?

[Alexander Malkis]

Assume we have somewhere
typedef enum foo { A,B,C } foo;

Is C+1 a constant expression?

[
I want to write smth. like
char* strs[C+1]={"Astr","Bstr" ,"Cstr"};
]

Could anyone help?
Regards,
Alex.
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[Mike Wahler]

Re: Is that a constant expression?


"Alexander Malkis" <alexmalk@LOESC HEDIESline.cs.u ni-sb.de> wrote in message
news:clcm-20040226-0017@plethora.n et...[color=blue]
> Assume we have somewhere
> typedef enum foo { A,B,C } foo;
>
> Is C+1 a constant expression?[/color]

Yes.
[color=blue]
>
> [
> I want to write smth. like
> char* strs[C+1]={"Astr","Bstr" ,"Cstr"};
> ]
>
> Could anyone help?[/color]

It looks OK to me. Are you having trouble with it?

-Mike

[Alex]

Re: Is that a constant expression?

No. Not yet.
Thank you.
Alex.

Mike Wahler wrote:[color=blue]
>
> "Alexander Malkis" <alexmalk@LOESC HEDIESline.cs.u ni-sb.de> wrote in message
> news:clcm-20040226-0017@plethora.n et...[color=green]
> > Assume we have somewhere
> > typedef enum foo { A,B,C } foo;
> >
> > Is C+1 a constant expression?[/color]
>
> Yes.
>[color=green]
> >
> > [
> > I want to write smth. like
> > char* strs[C+1]={"Astr","Bstr" ,"Cstr"};
> > ]
> >
> > Could anyone help?[/color]
>
> It looks OK to me. Are you having trouble with it?
>
> -Mike[/color]

[Dag Henriksson]

Re: Is that a constant expression?


"Alexander Malkis" <alexmalk@LOESC HEDIESline.cs.u ni-sb.de> skrev i
meddelandet news:clcm-20040226-0017@plethora.n et...[color=blue]
> Assume we have somewhere
> typedef enum foo { A,B,C } foo;
>
> Is C+1 a constant expression?
>[/color]

That depends.
If the built-in operator+ is used, it is. If you have written an own
operator+(foo, int), it isn't.

--
Dag Henriksson

[Leor Zolman]

Re: Is that a constant expression?

On 26 Feb 2004 21:56:14 GMT, Alexander Malkis
<alexmalk@LOESC HEDIESline.cs.u ni-sb.de> wrote:
[color=blue]
>Assume we have somewhere
>typedef enum foo { A,B,C } foo;
>
>Is C+1 a constant expression?[/color]

Yes.
[color=blue]
>
>[
>I want to write smth. like
>char* strs[C+1]={"Astr","Bstr" ,"Cstr"};
>]
>
>Could anyone help?[/color]

Well, you start up your text editor, and then type it in ;-)

Seriously, though, wouldn't just trying this in your compiler have been
less work than entering the names of all those newsgroups you've
cross-posted to?

[color=blue]
>Regards,
>Alex.[/color]

Leor Zolman
BD Software
leor@bdsoft.com
www.bdsoft.com -- On-Site Training in C/C++, Java, Perl & Unix
C++ users: Download BD Software's free STL Error Message
Decryptor at www.bdsoft.com/tools/stlfilt.html
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[Thomas Matthews]

Re: Is that a constant expression?

Alexander Malkis wrote:[color=blue]
> Assume we have somewhere
> typedef enum foo { A,B,C } foo;
>
> Is C+1 a constant expression?
>
> [
> I want to write smth. like
> char* strs[C+1]={"Astr","Bstr" ,"Cstr"};
> ]
>
> Could anyone help?
> Regards,
> Alex.[/color]

What's wrong with letting the compiler figure
out the number of elements?

char * strs[] = {"Astr", "Bstr", "Cstr"};

--
Thomas Matthews

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Other sites:
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http://www.sgi.com/tech/stl -- Standard Template Library
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[Jeff Schwab]

Re: Is that a constant expression?

Alexander Malkis wrote:
[color=blue]
> typedef enum foo { A,B,C } foo;[/color]

.....
[color=blue]
> char* strs[C+1]={"Astr","Bstr" ,"Cstr"};[/color]


NB: The following refers to C++. I don't know the answer in C.

Your approach almost certainly will work in this particular case.
However, it may not work in the general case. Enums are not guaranteed
to have any minimum number of bits, as long as they are wide enough to
hold all of their enumerators.

Here is a common alternative:

enum Foo { a, b, c, num_foo };

-Jeff
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[Hans-Bernhard Broeker]

Re: Is that a constant expression?

[F'up2 cut down --- should have been done by OP!]

In comp.lang.c.mod erated Alexander Malkis wrote:
[color=blue]
> Assume we have somewhere
> typedef enum foo { A,B,C } foo;[/color]
[color=blue]
> Is C+1 a constant expression?[/color]

Yes. What makes you suspect otherwise?
[color=blue]
> I want to write smth. like
> char* strs[C+1]={"Astr","Bstr" ,"Cstr"};[/color]

You don't need C+1 to be a constant, for that. Actually, you don't
need C+1 at all:

char *strs[] = {"Astr", "Bstr", "Cstr"};


--
Hans-Bernhard Broeker (broeker@physik .rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.
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[Dan Pop]

Re: Is that a constant expression?

In <clcm-20040226-0017@plethora.n et> Alexander Malkis <alexmalk@LOESC HEDIESline.cs.u ni-sb.de> writes:
[color=blue]
>Assume we have somewhere
>typedef enum foo { A,B,C } foo;
>
>Is C+1 a constant expression?[/color]

Yes.
[color=blue]
>[
>I want to write smth. like
>char* strs[C+1]={"Astr","Bstr" ,"Cstr"};
>][/color]

What's wrong with:

char *strs[] = {"Astr", "Bstr", "Cstr"};

?

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de
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[those who know me have no need of my name]

Re: Is that a constant expression?

[ugh -- horribly cross-posted and no followup-to]

in comp.lang.c.mod erated i read:
[color=blue]
>Assume we have somewhere
>typedef enum foo { A,B,C } foo;
>
>Is C+1 a constant expression?[/color]

yes.

--
a signature
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[Claus Reibenstein]

Re: Is that a constant expression?

Alexander Malkis schrieb:
[color=blue]
> Is C+1 a constant expression?[/color]

Where do you want to find the answer? I see no fup2. And obviously
no-one so far recognized your crossposting anyway. Poor blind guys.

Fup2 ... hmmm ... where? ... let's see ... yes, that seems adequate.

Claus
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[Tor Husabø]

Re: Is that a constant expression?

Jeff Schwab wrote:
[color=blue]
> Alexander Malkis wrote:
>[color=green]
>> typedef enum foo { A,B,C } foo;[/color]
>
>
> ....
>[color=green]
>> char* strs[C+1]={"Astr","Bstr" ,"Cstr"};[/color]
>
>
>
> NB: The following refers to C++. I don't know the answer in C.
>
> Your approach almost certainly will work in this particular case.
> However, it may not work in the general case. Enums are not guaranteed
> to have any minimum number of bits, as long as they are wide enough to
> hold all of their enumerators.[/color]

Just for the record, an enum in C, unlike in C++, is always an int. And
the size enum foo doesn't matter here anyway.

Tor
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[Jeff Schwab]

Re: Is that a constant expression?

Tor Husabø wrote:[color=blue]
> Jeff Schwab wrote:
>[color=green]
>> Alexander Malkis wrote:
>>[color=darkred]
>>> typedef enum foo { A,B,C } foo;[/color]
>>
>>
>>
>> ....
>>[color=darkred]
>>> char* strs[C+1]={"Astr","Bstr" ,"Cstr"};[/color]
>>
>>
>> NB: The following refers to C++. I don't know the answer in C.
>>
>> Your approach almost certainly will work in this particular case.
>> However, it may not work in the general case. Enums are not
>> guaranteed to have any minimum number of bits, as long as they are
>> wide enough to hold all of their enumerators.[/color]
>
>
> Just for the record, an enum in C, unlike in C++, is always an int. And
> the size enum foo doesn't matter here anyway.[/color]

Yes, you're right. Of course, if A, B, and C were macros representing
expressions with large initializers, or if int's were only one bit
wide... :)

It is true, though, that the size of the array doesn't need to be
specified explicitly here anyway.
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