From Thomas Lumley <thomas@biostat.washington.edu>  Wed Aug 20 18:34:35 1997
From: Thomas Lumley <thomas@biostat.washington.edu> (Thomas Lumley)
Date: Wed, 20 Aug 1997 10:34:35 -0700 (PDT)
Subject: R-alpha: R-0.50-a3(+) Method despatching bug ?
In-Reply-To: <199708201552.RAA02602@sophie.ethz.ch>
Message-ID: <Pine.SUN.3.95.970820094622.641B-100000@chekov>

On Wed, 20 Aug 1997, Martin Maechler wrote:

> It is very wierd...  Can some of you confirm the following behavior ?
> It is a new bug (feature ?)  which was not yet in 0.49 ...
>

I'm not sure that you can expect NextMethod to work if you fiddle with the
class list...

However, there is still something wrong with method dispatching, since
print.noquote <- function (obj, ...)  NextMethod(quote = FALSE,...)
doesn't work either.  The error occurs when R tries for some reason to
make a recursive call to print.noquote.

Using debug() also shows the interesting fact that
R> nq 
calls print() with its arguments evaluated
------
debugging in: print(structure(c("a", "b", "c", "d", "e", "f", "g", "h",
"i", 
"j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", 
"w", "x", "y", "z"), class = "noquote"))
debugging in: print.noquote(structure(c("a", "b", "c", "d", "e", "f", "g", 
"h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", 
"u", "v", "w", "x", "y", "z"), class = "noquote"))
Error: couldn't find function "print.noquote"
-------
but
----------
R> print(nq)
 print(nq)
debugging in: print(nq)
debugging in: print.noquote(nq)
 [1] a b c d e f g h i j k l m n o p q r s t u v w x y z
attr(,"class")
[1] noquote
exiting from: print.noquote(nq)
exiting from: print(nq)
----------
doesn't evaluate the argument first.




Thomas Lumley
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R-alpha: R-0.50-a3(+) Method despatching bug ?
Thomas Lumley