Syntactically valid names - R-devel

Hadley Wickham · 2011-07-05T22:29:39Z

> I wouldn't expect so. The basic structure might be handled using a regexp of sorts, but even that is tricky because of the "dot not followed by number" rule, and then there's the stop list of reserved words, which would make your code clumsy whatever you do. > > How on Earth would you expect anything to be significantly more elegant than your > > function(x) x == make.names(x) > > anyway??! (OK, if there was a wrapper for the C level isValidName() function...) Good point. Thanks! Hadley --

Hadley Wickham

Tue, Jul 5, 2011 3:29 PM #

Good point.  Thanks!

Hadley

Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/

steven mosher

Tue, Jul 5, 2011 4:31 PM #

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Hadley Wickham

Tue, Jul 5, 2011 4:40 PM #

On Tue, Jul 5, 2011 at 7:31 PM, steven mosher <moshersteven at gmail.com> wrote:

Hmm, I think that suggests a couple of small bug in make.names:

[1] "..."

[1] "..1"

and

[1] TRUE


Hadley

Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/

Peter Dalgaard

Tue, Jul 5, 2011 5:22 PM #

On Jul 6, 2011, at 01:40 , Hadley Wickham wrote:

What's wrong with that? They are names alright, just with special meanings.

[1] "name"

Mildly insane, but technically OK, no?

Peter Dalgaard
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

Hadley Wickham

Tue, Jul 5, 2011 6:25 PM #

But you can't really use them for variables:

Error: '...' used in an incorrect context

Error: 'nthcdr' needs a list to CDR down

And make.names generally protects you against that:

[1] "function."

[1] "break."

[1] "TRUE."

I don't think so:

Error in assign(x, 1) : variable names are limited to 10000 bytes

Hadley

Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/

Peter Dalgaard

Wed, Jul 6, 2011 1:10 AM #

On Jul 6, 2011, at 03:25 , Hadley Wickham wrote:

That's two different issues:

Error: unexpected 'break' in "y$break"

Notice that there is nothing _syntactically_ wrong with ... & friends as names:

... <- 4

It's the _evaluator_ that throws the error because the ...-name has a special interpretation.

But that's a sanity check, with an arbitrary cutoff.  A string of a million "x"s is syntactically a valid name, it's just the evaluator that refuses to play with it. (Not to say that it would be wrong to put in a similar sanity check in make.names.)

Peter Dalgaard
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

Hadley Wickham

Wed, Jul 6, 2011 5:58 AM #

Oh good point.  Thanks for the clarification.

Hadley

Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/