Assignment operators (was [R] modifying a vector)

[ripley@stats.ox.ac.uk]

On Mon, 1 Jul 2002 Mark.Bravington@csiro.au wrote:

> Bill Venables expected howls of protest about deprecation of underscore for
> assign. Here's my one-and-only howl on this point:
>
> (1) I don't like <- as an assignment operator, because it creates an
> ambiguity with comparisons: I can write "x+1", "x-1", "x<1" but not "x<-1".
> However, I guess it's a bit much to expect the entire R/S community to do
> away with "<-" in favour of "_" or Delphi (Pascal) notation ":=", much as it
> would delight me; so we're stuck with <- I guess.
>
> (2) "_" strikes me as completely unambiguous. It means assignment, and
> that's all it means. For my money, that's more important than aesthetics.
> Anyway, if you choose a nice colourscheme, the _ doesn't look that bad. Me,
> I like green.
>
> (3) for my remaining bit of money, "=" should not be allowed at all as an
> assignment operator: S made a mistake but R doesn't have to.
> "="-as-assignment has to be hedged with all sorts of conditions to prevent
> ambiguities, and to have an operator which frequently can't be used doesn't
> seem helpful. Having it "grudgingly available to the cognoscenti" is not all
> that much better!
>
> (4) If deprecation is the first step on the road to removal and to "_" being
> allowed in unquoted variable names, then that would be tiresome. I have many
> hundreds of functions spanning thousands of lines of S/R code, filled with
> "_"s. I really don't want to spend time changing all of them just to solve a
> non-problem in R. Which is, I should emphasize, a wonderful piece of
> software.

There is a simple solution: use the procedures which have long been
described in `Writing R Extensions' to turn your code into properly
formatted canonical code.  (That turns all left-assignments into
`<-', since that is the canonical form.).

It may be a non-problem for you, but it was for the original poster in
the original thread.

-- 
Brian D. Ripley,                  ripley@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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