enum

[adrian suri]

Hi

playing with enum, for example system DosCall return int values for disk
partition so say I use an enum

#include <iostream>

using namespace std;
int main()
{
enum drv { A=1, B, C,D,E,F,G,H,I,J ,K,L,M,N,O,P };

char dv=drv(1);
cout <<dv;
}

how can I get the letter from the number value char dv=drv(1); does not
work, or is it best to use an array of char instead

adrian

[Bob Hairgrove]

Re: enum

On Thu, 16 Feb 2006 15:49:33 +0100, adrian suri <asuri@tele2.se >
wrote:
[color=blue]
>Hi
>
>playing with enum, for example system DosCall return int values for disk
>partition so say I use an enum
>
>#include <iostream>
>
>using namespace std;
>int main()
>{
>enum drv { A=1, B, C,D,E,F,G,H,I,J ,K,L,M,N,O,P };
>
>char dv=drv(1);
>cout <<dv;
>}
>
>how can I get the letter from the number value char dv=drv(1); does not
>work, or is it best to use an array of char instead
>
>adrian[/color]

Maybe like this?

enum drv { A='A', B, C,D,E,F,G,H,I,J ,K,L,M,N,O,P };

Actually, an array would probably serve you better because with an
enum, you can't do "drv(1)"

--
Bob Hairgrove
NoSpamPlease@Ho me.com

[Ivan Vecerina]

Re: enum

"adrian suri" <asuri@tele2.se > wrote in message
news:Yh0Jf.8$Ox 5.34@nntpserver .swip.net...
: Hi
:
: playing with enum, for example system DosCall return int values for disk
: partition so say I use an enum
:
: #include <iostream>
:
: using namespace std;
: int main()
: {
: enum drv { A=1, B, C,D,E,F,G,H,I,J ,K,L,M,N,O,P };
:
: char dv=drv(1);
: cout <<dv;
: }

In the above code, you actually cast the enum value to a char
(ie. as if you are specifying its ASCII value), then try to
print it. And character values <0x20 are not printable.

But anyway, in C++, enums just print as integers.
Enum-defined identifiers are only useful within
the source code.

: how can I get the letter from the number value char dv=drv(1); does not
: work, or is it best to use an array of char instead

On an ASCII-based platform, you could write:
int driveNb = 3;
cout << ( ('A'-1)+driveNb ); // prints 'C'

Using an array of char, as you suggested, will indeed be more portable:
char const drvIdMap[] = ".ABCDEFGHIJKLM NOPQRSTUVWXYZ";
int driveNb = 3;
cout << drvIdMap[driveNb]; // prints 'C'


Ivan
--
http://ivan.vecerina.com/contact/?subject=NG_POST <- email contact form
Brainbench MVP for C++ <> http://www.brainbench.com

[Victor Bazarov]

Re: enum

adrian suri wrote:[color=blue]
> playing with enum, for example system DosCall return int values for disk
> partition so say I use an enum
>
> #include <iostream>
>
> using namespace std;
> int main()
> {
> enum drv { A=1, B, C,D,E,F,G,H,I,J ,K,L,M,N,O,P };
>
> char dv=drv(1);
> cout <<dv;
> }
>
> how can I get the letter from the number value char dv=drv(1); does not
> work, or is it best to use an array of char instead[/color]

There is no "letter" at run-time. The "letter" exists only in your code.
You need to write your own conversion from 'drv' to 'char' if you need to
get the "letter". Of course, a simpler way would be to get the value and
simply add 'A' to it after subtracting 1:

char dv = whatever -1 + 'A';

Now, 1 would be mapped to 'A', 2 to 'B' and so on.

V
--
Please remove capital As from my address when replying by mail

[Richard Herring]

Re: enum

In message <Yh0Jf.8$Ox5.34 @nntpserver.swi p.net>, adrian suri
<asuri@tele2.se > writes[color=blue]
>Hi
>
>playing with enum, for example system DosCall return int values for disk
>partition so say I use an enum
>
>#include <iostream>
>
>using namespace std;
>int main()
>{
>enum drv { A=1, B, C,D,E,F,G,H,I,J ,K,L,M,N,O,P };
>
>char dv=drv(1);
>cout <<dv;
>}
>
>how can I get the letter from the number value[/color]

You can't. The source-code names of C++ objects are not available at
runtime.
[color=blue]
>char dv=drv(1); does not
>work, or is it best to use an array of char instead[/color]

Yes, if the numerical values are consecutive and bounded.

If not, you might be better off using a std::map<int, char>.

--
Richard Herring