From fharrell@virginia.edu  Sun Jun 30 19:42:49 2002
From: fharrell@virginia.edu (Frank E Harrell Jr)
Date: Sun, 30 Jun 2002 14:42:49 -0400
Subject: Assignment operators (was [R] modifying a vector)
In-Reply-To: <Pine.LNX.4.31.0206301835430.1814-100000@gannet.stats>
References: <20020630124930.1820aaf1.fharrell@virginia.edu>
 <Pine.LNX.4.31.0206301835430.1814-100000@gannet.stats>
Message-ID: <20020630144249.21739e6e.fharrell@virginia.edu>

On Sun, 30 Jun 2002 18:57:38 +0100 (BST)
ripley@stats.ox.ac.uk wrote:

> On Sun, 30 Jun 2002, Frank E Harrell Jr wrote:
> 
> > On 30 Jun 2002 09:12:31 -0700
> > "A.J. Rossini" <rossini@blindglobe.net> wrote:
> >
> > > >>>>> "john" == John Fox <jfox@mcmail.cis.mcmaster.ca> writes:
> > >
> > >     john> The equal sign has already been provided as an alternative assignment
> > >     john> operator in R.
> > >
> > > And I feel the same way about "=" as I do about "_".  Yech.
> >
> > I'll second that.  And we've already seen the big trouble that can be
> caused by "=" (e.g., mistyping sex=='male' as sex='male') that was not
> envisioned by the developers.  -Frank Harrell
> 
> Frank,
> 
> Was that actually in R (where very few people use =)?  Unlike S4, = is not
> a general-purpose assignment operator, and this sort of thing *was*
> `envisioned by the developers'.  For example, if(sex = "male") is a syntax
> error in R.  (Some more insidious ones, such as using assignment in the
> a function call, are also disallowed.)

It was probably S-Plus.  I have trouble keeping S-Plus and R separate sometimes.
I hope that R also provides safeguards about "=" when it appears in an argument to a function.

> 
> If there is evidence that this is regularly causing trouble we would want
> to re-consider its scope, but the availability of `=' is hardly publicised
> (and not even the editor of the Programmer's Niche remembered about it).
> 
> Brian
> 
> (Moved to R-devel, as maybe R-help should be spared this source of
> confusion.)

Sure.  Thanks Brian  -Frank

> 
> -- 
> 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
> 


-- 
Frank E Harrell Jr              Prof. of Biostatistics & Statistics
Div. of Biostatistics & Epidem. Dept. of Health Evaluation Sciences
U. Virginia School of Medicine  http://hesweb1.med.virginia.edu/biostat
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Assignment operators (was [R] modifying a vector)
Frank E Harrell Jr