Re: [YANG] 7.6, default value for a type

On Fri, Jan 11, 2008 at 04:27:13PM -0800, Andy Bierman wrote:

> Sec 7.6, para 5 says:
>
>    If a leaf has a "default" statement, the leaf's default value is set
>    to the value of the "default" statement.  Otherwise, if the leaf's
>    type has a default value, and the leaf is not mandatory, then the
>    leaf's default value is set to the type's default value.  In all
>    other cases, the leaf does not have a default value.
>
> The default value for each builtin type is not defined anywhere.
> This is a nice detail, and covers things like the agent creating
> a bunch of counter objects or ifOperStatus objects.
>
> It mandates that a specific value will be used, not random values.
>
> What are the specific values?
>
>   - int8 to uint64: 0
>   - float32, float64: 0.0
>   - string, binary, instance-identifier: empty string
>   - enumeration:  ???  (!) [first value?]
>   - boolean: false
>   - bits: empty bitset
>   - keyref:  default for data type of 'path'

Why not leave it undefined? It is easy to define defaults:

   typedef int8-zero {
       type int8;
       default 0;
   }

If we hard wire defaults, it will be a pain to define a type which
does not have a default, e.g. for an SNMP counter.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>

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