From dsmith@insightful.com  Tue Apr 10 19:50:17 2001
From: dsmith@insightful.com (David M Smith)
Date: Tue, 10 Apr 2001 11:50:17 -0700
Subject: [Rd] Segmentation fault in subscripting array of lists (PR#904)
In-Reply-To: <200104101401.QAA23458@pubhealth.ku.dk>
Message-ID: <LGEFIDJJDBKMHCAKBCOIIEBBCPAA.dsmith@insightful.com>

R clearly shouldn't crash, but tmp[[1, ]] is semantically incorrect.  The
result of "[[" is required to be a single value from a vector (or generally,
an array) of the mode of the vector.  To select more than one element from
an array, you must use "[".  The results from S-PLUS 6 are:

> tmp[[1,  ]]
Problem in [[: Attempt to select more than one element: structure(list(NULL,
NULL, NULL, list(fred = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)), NULL, NUL....
Use traceback() to see the call stack

This error message indicates the error.  Using "[" gives the correct result:

> tmp[1,  ]
[[1]]:
NULL

[[2]]:
[[2]]$fred:
 [1]  1  2  3  4  5  6  7  8  9 10


[[3]]:
NULL

[[4]]:
NULL


# David Smith

--
David M Smith <dsmith@insightful.com>
S-PLUS Product Marketing Manager, Insightful Corp, Seattle WA
Tel: +1 (206) 283 8802 x360
Fax: +1 (206) 283 0347

MathSoft is now Insightful!  See www.insightful.com for details.

> -----Original Message-----
> From: owner-r-devel@stat.math.ethz.ch
> [mailto:owner-r-devel@stat.math.ethz.ch]On Behalf Of
> J.C.Rougier@durham.ac.uk
> Sent: Tuesday, April 10, 2001 07:02
> To: r-devel@stat.math.ethz.ch
> Cc: R-bugs@biostat.ku.dk
> Subject: [Rd] Segmentation fault in subscripting array of lists (PR#904)
>
>
> I get a segmentation fault as follows:
>
> > tmp <- array(list(), c(3, 4))
> > tmp[[1, 2]]
> NULL                                  # as expected
> > tmp[[1, 2]]$fred <- 1:10
> > tmp                                 # as expected
>      [,1]   [,2]     [,3]   [,4]
> [1,] "NULL" "List,1" "NULL" "NULL"
> [2,] "NULL" "NULL"   "NULL" "NULL"
> [3,] "NULL" "NULL"   "NULL" "NULL"
> > tmp[[1, 2]]                         # as expected
> $fred
>  [1]  1  2  3  4  5  6  7  8  9 10
>
> > tmp[[1, ]]                          # whoops!
> Segmentation fault
>
> Cheers, Jonathan.
>
> --please do not edit the information below--
>
> Version:
>  platform = sparc-sun-solaris2.7
>  arch = sparc
>  os = solaris2.7
>  system = sparc, solaris2.7
>  status =
>  major = 1
>  minor = 2.1
>  year = 2001
>  month = 01
>  day = 15
>  language = R
>
> Search Path:
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[Rd] Segmentation fault in subscripting array of lists (PR#904)
David M Smith