Re: [Rd] attach behavior

From: Peter Dalgaard <>
Date: Sun 29 Aug 2004 - 17:26:08 EST

Prof Brian D Ripley <> writes:

> On Sun, 29 Aug 2004, Erich Neuwirth wrote:
> > In R 1.9.1, attaching an object more than once puts the object's name on
> > the search path more than once also. Therefore, to remove it, one has to
> > detach it multiply.
> > Wouldn'tn it make sense to change the behavior of attach in a way
> > that object names are not added to the search path more than once?
> They need not be the same object, so no. It's quite common practice to
> modify an object, attach it temporarily and detach it again. I suspect
> that people using attach() frequently should be thinking more in terms of
> with().

That's one argument. Another is that attach(foo) followed by detach() should leave the search path unchanged. I.e. if attach() is sometimes a NOP, we must arrange so that the next detach() is one too. You could do that I suppose, but then there's code that acts depending on what it finds in search(), and...

Or, briefly: That way lies madness!

   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (             FAX: (+45) 35327907

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