Re: [dylan] float-invalid proposal

For reference, this is done for HARP on all platforms that HARP supports:

  https://github.com/dylan-lang/opendylan/pull/642

 - Bruce


On Mon, Jan 6, 2014 at 9:28 AM, Bruce Mitchener
<[email protected]>wrote:

> On Mon, Jan 6, 2014 at 3:16 AM, Dustin Voss <[email protected]> wrote:
>
>> The DRM already says that “/” can signal an error for division by zero,
>> so we don’t *need* to alter the language spec by adding
>> *<arithmetic-domain-error>*. That said, I think it would be fine to
>> elevate this particular condition above all the others in the DRM where it
>> just says “blah-blah-blah signals an error.”
>>
>> If we proceed, I suggest the following:
>>
>>
>>    - *<arithmetic-domain-error>* inherits from *<serious-condition>,*not
>>    *<error>*. I think it is more akin to a network problem (given as an
>>    example of *<serious-condition>*) than to a *<type-error>* (an
>>    example of an *<error>*).
>>    - It should have a recovery protocol:
>>       - A condition handler can return a value. The runtime will use
>>       that returned value as a substitute result for the failed operation.
>>       - The runtime will not establish a *<restart>* handler.
>>
>>
> The DRM doesn't specify the error or the error hierarchy involved for a
> division by zero, just that an error is signaled.
>
> An invalid floating point exception happens for things like 0/0, Infinity
> - Infinity, and so on.  These aren't much different from a division by
> zero.  I don't think it should have some other parent, these should all be
> <arithmetic-error>.
>
> In Haskell (for example), these all have the same parent (FloatException).
>
> I think there's room for improving floating point control, like allowing
> setting the rounding mode, in some other extensions, but adding the
> float-invalid stuff that prom did is pretty straight forward (and doesn't
> really involve modifying the DRM since the DRM doesn't comment much on this
> subject).
>
>  - Bruce
>
>

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