(fwd) Re: [R] the underscore ("_") in variable name

Prof Brian Ripley ripley at stats.ox.ac.uk
Tue Oct 3 16:05:19 CEST 2000

> Date: Tue, 03 Oct 2000 14:45:32 +0000
> From: Alberto Murta <amurta at ipimar.pt>
> Duncan Murdoch wrote:
> > I don't follow this argument.  Underscore isn't used anywhere else in
> > the language, so when you see one, you know it's an assignment.  On
> > the other hand, both "<" and "-" have multiple other uses.  This leads
> > to lots of possibilities for confusion:
> >
> >   x <--5
> >   x < -5
> >   x <- 5
> Those are classic examples. Nevertheless, "<-" is more appealing visually than 
> as an assignment operator, mainly because "_"  is used in file and variable 
> in other programming languages.
> > (Of course, I actually prefer the Pascalian :=, but I realize that
> > puts me in a double minority :-).
> >
> Here I agree with you. I think that future releases of R should have "=" as 
> assignement operator, just like the last version of S.

Note, "=" is *one of* the allowed assignment operators in Svr4, but not
*the* assignment operator and it is only allowed where it would not
lead to ambiguities.  If you take your S code and globally substitute
"=" for "<-" you are likely to find it badly broken.  Bill Venables and
I did go down that route at one time, but after we discovered that we
just did not stop using "=" where it did not work as assignment, we
gave up.  "<-" is the preferred assignment operator in S-PLUS 5.x and
6.x, with good reasons.  This is much subtler than the inaccurate typing
earlier in this thread.

(I'll leave John Chambers to comment if `the last version of S' has yet

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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