coding

[steven james]

Greetings,

It seems to me that working out the integer value of an enum is actually
abuse of the type. The closest one should get to that is ++ or -- to step
through enumerated objects.

Of course, nobody ever takes liberties with that, especially me :-)

If the value itself is significant, it should probably be a define. If
it's only significant for ABI compatibility, best practice is to only add
to the end of the list and retain deprecated enums until an ABI breaking
version change happens. A comma after the last enum value is a pretty
decent invitation to do the right thing.

G'day,
sjames




On Tue, 2 Sep 2003, Greg Watson wrote:

> At 1:32 PM -0600 2/9/03, ron minnich wrote:
> >anybody object to anonymous enums? I've gotten used to them in Plan 9 and
> >like them. Instead of this:
> >
> >#define FLOPPY_DEVICE   0
> >#define PARALLEL_DEVICE 1
> >#define COM2_DEVICE     2
> >#define COM1_DEVICE     3
> >#define SWC_DEVICE      4
> >#define MOUSE_DEVICE    5
> >#define KBC_DEVICE      6
> >#define GPIO_DEVICE     7
> >#define ACB_DEVICE      8
> >#define FSCM_DEVICE     9
> >#define WDT_DEVICE     10
> >
> >you get this:
> >enum {
> >  FLOPPY_DEVICE=0,
> >  PARALLEL_DEVICE,
> >  COM2_DEVICE,   
> >  COM1_DEVICE,   
> >  SWC_DEVICE,    
> >  MOUSE_DEVICE,  
> >  KBC_DEVICE,    
> >  GPIO_DEVICE,   
> >  ACB_DEVICE,    
> >  FSCM_DEVICE,   
> >  WDT_DEVICE
> >};
> >
> >The advantages I see
> >- somewhat less prone to error
> >- looks nicer
> >- the big one: enums are first-class objects to the compiler, and
> >   #defines are pertty much ripped out by the compiler and disappear
> >   into constant numbers.
> >
> >
> >comments?
> >
> >ron
> 
> I think they work well when you have a sequence of numbers like this, 
> but I would rather see each enum explicitly given it's value as in:
> 
> enum {
>   FLOPPY_DEVICE=0,
>   PARALLEL_DEVICE=1,
>   COM2_DEVICE=2,
>   COM1_DEVICE=3,
>   SWC_DEVICE=4,
>   MOUSE_DEVICE=5,
>   KBC_DEVICE=6,
>   GPIO_DEVICE=7,
>   ACB_DEVICE=8,
>   FSCM_DEVICE=9,
>   WDT_DEVICE=10
> };
> 
> Otherwise you're forever trying to work out what the actual value is.
> 
> Where it doesn't work is when you have a bunch of random defines with 
> unrelated values, or values that jump about all over the place.
> 
> Greg
> 
> _______________________________________________
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> 

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-------------------------steven james, director of research, linux labs
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