howto: rotate a ring

howto: rotate a ring

[T. V. Raman]

The documentation for ring.el implies that there must be a
ring-rotate function -- but there doesn't appear to be an
explicit ring-rotate function?

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--raman

      
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Re: howto: rotate a ring

[Karl Fogel]

"T. V. Raman" <raman@users.sf.net> writes:
> The documentation for ring.el implies that there must be a
> ring-rotate function -- but there doesn't appear to be an
> explicit ring-rotate function?

Indeed.  I don't see anything either -- I think the documentation is
just wrong.  Maybe it's referring to the wraparound property of rings
(that if you pass too high an index, the appropriate modulo will be
performed, that sort of thing).

Do you need `ring-rotate', or can we just remove that bit from the
documentation?

-Karl

RE: howto: rotate a ring

[Drew Adams]

> > The documentation for ring.el implies that there must be a
> > ring-rotate function -- but there doesn't appear to be an
> > explicit ring-rotate function?
> 
> Indeed.  I don't see anything either -- I think the documentation is
> just wrong.  Maybe it's referring to the wraparound property of rings
> (that if you pass too high an index, the appropriate modulo will be
> performed, that sort of thing).
> 
> Do you need `ring-rotate', or can we just remove that bit from the
> documentation?

If by "rotate" is meant traverse the ring in either direction, then there
are functions to do that, `ring-next' and `ring-previous'. However, I see
that the doc lists both rotation and traversal operations. To me, they are
the same thing, since a ring is circular (turn the ring = advance along it).

I sent a ring.el patch on 2007-10-08 with those functions. Richard installed
it on 2007-10-14:

Revision 1.26 - (view) (download) (annotate) - [select for diffs] 
Sun Oct 14 22:52:59 2007 UTC (4 months, 2 weeks ago) by rms 
Branch: MAIN 
Changes since 1.25: +72 -0 lines 
Diff to previous 1.25 
(ring-convert-sequence-to-ring)
(ring-insert+extend, ring-remove+insert+extend, ring-member)
(ring-next, ring-previous): New functions.