[R] about the char _

Prof Brian D Ripley ripley at stats.ox.ac.uk
Sat Oct 6 10:54:39 CEST 2001

For clarity, can we note that there are two issues here?

1) Should "_" be allowed for assignment?   Currently "<-" and "->" and "_"
and (in R-devel only, in some circumstances) "=" are allowed.

2) Should "_" be allowed in names.  This falls into two parts.
a) should it be allowed in bare names (unquoted)
b) should it be allowed in non-standard (quoted) names.

Now 2a implies not-1, but there are a lot of other possibilities.

Even if we change 1 to "no" (which I have advocated), I think allowing 2a
would be very confusing to experienced users.  And several correspondents
are asking for 2a, not to change 1.

On Fri, 5 Oct 2001, Fan wrote:

> 1. I totally agree with the idea of maintaining back compatibility,
> my question was: "is there an option to change this behaviour"
> (locally or globally). An option will be the only way to satisfy everyone.
> 2. I'm little surprised of the discussions followed in this thread:
> my question was not a theoritical langugage concern (like the operator
> assignment, lazeiness, etc.), or a conversion feasability (like make.names,
> use of ""), but rather the following issue:
>   "how to maintain the same variable names in different systems"
> --
> Fan
> ps: the origin of the assignment in S comed from APL,
> the first array or vector oriented language.

Well, JMC can comment on that.  I understood from Rick Becker that long
long ago AT&T had terminals with a left-arrow key and that was the original
S assignment symbol.  I less clearly remember being told that it generated
the ASCII code for _.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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