For my particular project (it binds with something like finite state machine) I will write some counterpart of decode function from std.utf. Future function will decode string backward, return dchar and change index passed by reference.

Is it interesting for community that I code this feature in general way targeting in phobos for future?

On Tuesday, 6 January 2015 at 06:43:13 UTC, HaraldZealot wrote:
> For my particular project (it binds with something like finite state machine) I will write some counterpart of decode function from std.utf. Future function will decode string backward, return dchar and change index passed by reference.
>
> Is it interesting for community that I code this feature in general way targeting in phobos for future?

For UTF, there's already std.utf.strideBack which does most of the work. I don't know why there is no std.utf.decodeBack - should be very simple to wrap over strideBack.

However, for grapheme clusters, there isn't yet a counterpart for std.uni.graphemeStride/decodeGrapheme, which notably affects std.uni.byGrapheme, which is currently not a bidirectional range. Any improvement would be much appreciated.

On Tuesday, January 06, 2015 08:09:57 Jakob Ovrum via Digitalmars-d wrote:
> On Tuesday, 6 January 2015 at 06:43:13 UTC, HaraldZealot wrote:
> > For my particular project (it binds with something like finite state machine) I will write some counterpart of decode function from std.utf. Future function will decode string backward, return dchar and change index passed by reference.
> >
> > Is it interesting for community that I code this feature in general way targeting in phobos for future?
>
> For UTF, there's already std.utf.strideBack which does most of the work. I don't know why there is no std.utf.decodeBack - should be very simple to wrap over strideBack.

I'm pretty sure that you basically have to do what strideBack does before you can decode a code point, so all decodeBack would do would be to do exactly what back already does for strings, which is to use strideBack followed by decode.

- Jonathan M Davis

> I'm pretty sure that you basically have to do what strideBack does before
> you can decode a code point, so all decodeBack would do would be to do
> exactly what back already does for strings, which is to use strideBack
> followed by decode.
>
> - Jonathan M Davis

I have to read more attentively std.utf, but strideBack seems very suitable for me.

Thanks you both!!!

On 1/5/15 10:43 PM, HaraldZealot wrote:
> For my particular project (it binds with something like finite state
> machine) I will write some counterpart of decode function from std.utf.
> Future function will decode string backward, return dchar and change
> index passed by reference.
>
> Is it interesting for community that I code this feature in general way
> targeting in phobos for future?

back() and popBack() for narrow strings do reverse decode. -- Andrei

On Tuesday, 6 January 2015 at 16:58:24 UTC, Andrei Alexandrescu wrote:
> On 1/5/15 10:43 PM, HaraldZealot wrote:
>> For my particular project (it binds with something like finite state
>> machine) I will write some counterpart of decode function from std.utf.
>> Future function will decode string backward, return dchar and change
>> index passed by reference.
>>
>> Is it interesting for community that I code this feature in general way
>> targeting in phobos for future?
>
> back() and popBack() for narrow strings do reverse decode. -- Andrei

I need reverse decode from any position, not only from the last.
I have coded a litle with stideBack allready, it works. But usage isn't clear as could: first strideBack, then decode, and decode move index forward, then I have to strideBack again :)

Perhaps i will wrap such algorithm in some function, but an other side i will be forced to optimize that and write real decodeBack function.