Re: Creating a coding system

[David Kastrup <dak@gnu.org>]

handa@gnu.org (K. Handa) writes:

> In article <87h9wmd8ey.fsf@fencepost.gnu.org>, David Kastrup <dak@gnu.org> writes:
>> > The other method is to use CCL (i.e :coding-type 'ccl), but,
>> > if the combination of the charset decoding and translation
>> > table works, it's faster than running CCL code.
>
>> The translation table is not happy about translating things to nothing.
>> Apparently that makes the calculation of the reverse translation go
>> wrong.
>
> Ah, perhaps make-translation-table-from-alist should have
> optional argument to suppress building of reverse map, say
> no-reverse-mmap.  Just for decoding, we don't need a reverse
> map.

Whether we need it or not, empty productions should just be allowed and
ignored for reverse translation.  Of course, they are not compatible
with lossless conversions, but so are many other rules.

-- 
David Kastrup