R help - Jan 2011 - unicode variable and function names?

Dear List,


Is it possible to have function names like ? (unicode universal quantifier)?
This question is inspired by agda source code, which supports this.

http://www.cs.nott.ac.uk/~nad/listings/lib-0.4/Algebra.html

It would be handy to use. My guess is, however, that it's not supportet in
R.

Regards,
Steve

On Jan 3, 2011, at 7:44 PM, stvienna wiener wrote:
> Dear List,
>
>
> Is it possible to have function names like ? (unicode universal  
> quantifier)?
> This question is inspired by agda source code, which supports this.
>
> http://www.cs.nott.ac.uk/~nad/listings/lib-0.4/Algebra.html
>
> It would be handy to use. My guess is, however, that it's not  
> supportet in R.
If you are willing continue to call it as `?` rather than s just ?,  
then it seems to "work as expected".

 > `?` <- function(x) {x+1}
 >
 > `?`( c(1,2,3) )
[1] 2 3 4

Efforts to use the un-backquoted variants were failures for me:

 > ? <- function(x) {x+1}
Error: unexpected input in "?"

(Question: does your keyboard support such a character??? I.e,  Why  
would this be "handy"?)


-- 

David Winsemius, MD
West Hartford, CT

On 11-01-03 7:44 PM, stvienna wiener wrote:
> Dear List,
>
>
> Is it possible to have function names like ? (unicode universal
quantifier)?
> This question is inspired by agda source code, which supports this.
>
> http://www.cs.nott.ac.uk/~nad/listings/lib-0.4/Algebra.html
>
> It would be handy to use. My guess is, however, that it's not supportet
in R.
Why not just try it?  I get this:

 > ? <- 1
Error: unexpected input in "?"
 > `?` <- 1

i.e. it is seen as a non-syntactic name, so needs backquotes to be used, 
but then it's fine (except it's probably a bad idea, since non-UTF8 
systems will have trouble with it).  Looks like the error message needs 
fixing.

I was surprised how hard it was to find this documented, but it is there 
in the Introduction to R manual in section 1.8,  "R commands, case 
sensitivity, etc."  Someday someone should add this to the Language 
Definition manual.  The rule is that syntactic names need to start with 
. or a letter, and contain only letters, digits, . and _.  The confusing 
part is that "letter" doesn't have a universal definition, so the
manual
suggests limiting them to ASCII letters.

Duncan Murdoch