Re: [PATCH] pkl: Add exception_new to register user-defined exceptions

[Jose E. Marchesi]

>> > This commit introduces a new function `exception_new` to give an
>> > `Exception` value with a unique `code` number.
>> > (Based on your suggestion a while ago in IRC).
>> 
>> I like the approach.
>> 
>> However, this couples the contents of exceptions with the
>> `exception_new' generator.
>> 
>> What is really generated is the exception code, so what about having an
>> `exception_code' generator.  User-defined exceptions would then be
>> defined like:
>> 
>> var E_my_exception = Exception { code = exception_new, ... };
>> 
>> WDYT?
>> 
>
> I considered both approaches and chose the approach that I thought
> is more user-friendly.
> User just wants to define a new exception and don't need to be concerned
> about the `code` field.

Well, users can already build exceptions using standard codes, like:

      raise Exception {code = EC_generic,
                       msg = "unknown option -" + arg};

So generally speaking they should be aware of codes.  All the other
fields of an Exception have default values, so the user doesn't need to
be concerned with them.  I think that's enough abstraction.

> But OK, I'll send the new patch soon.

Thanks!