On 14-03-27 3:01 PM, Kevin Ushey wrote:
I too think it would be useful if R exported some version of its
string sorting routines, since sorting strings while respecting
locale, and doing so in a portable fashion while respecting the user's
environment, is not trivial. R holds a fast, portable, well-tested
solution, and I think package developers would be very appreciative if
some portion of this was exposed at the C level.
It does. You can put your strings in an R STRSXP vector, and call the R
sort function on it.
The usual objection to constructing an R expression and evaluating it is
that it is slow, but if you are talking about sorting, the time spent in
the sort is likely to dominate the time spent in the setup.
If not `Scollate`, then perhaps other candidates could be the more
generic `sortVector`, or the more string-specific (and NA-respecting)
`scmp`.
Evaluating an R expression gives you sortVector.
I can see an argument for Scollate being useful (sorting isn't the only
reason to compare strings), but I can see arguments against exposing it
too. Take a look at the source: it needs to be used carefully. In
particular, it can return a 0 for unequal strings, and users are likely
to get messed up by that, or to submit bogus bug reports. And it's not
impossible to work around: if you can collect the universe of strings to
compare in advance, then just use order() to convert them to integer
values, and compare those.
Duncan Murdoch
I understand that the volunteers at R Core have limited time and
resources, and exposing an API imposes additional maintenance burdens
on an already thinly stretched team, but this is a situation where the
R users and package authors alike could benefit. Or, if there are
other reasons why exporting such routines is not possible nor
recommended, it would be very informative to know why.
Thanks,
Kevin
On Thu, Mar 27, 2014 at 11:08 AM, Dirk Eddelbuettel <e...@debian.org> wrote:
On 26 March 2014 at 19:09, Romain François wrote:
| That's one part of the problem. Indeed I'd rather use something rather than
| copy and paste it and run the risk of being outdated. The answer to that is
We all would. But "they" won't let us by refusing to create more API access
points.
| testing though. I can develop a test suite that can let me know I'm out of
Correct.
| date and I need to copy and paste some new code, etc ... Done that before,
this
| is tedious, but so what.
|
| The other part of the problem (the real part of the problem actually) is that,
| at least when R is built with ICU support, Scollate will depend on a the
| collator pointer in util.c
| https://github.com/wch/r-source/blob/trunk/src/main/util.c#L1777
|
| And this can be controlled by the base::icuSetCollate function. Of course the
| collator pointer is not public.
So the next (and even less pleasant) answer is to build a new package which
links to, (or worse yet, embeds) libicu.
As you want ICU behaviour, you will need ICU code.
Dirk
--
Dirk Eddelbuettel | e...@debian.org | http://dirk.eddelbuettel.com
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