On Wed, 20 Sep 2006, Prof Brian Ripley wrote:
> On Wed, 20 Sep 2006, Parlamis Franklin wrote:
>
>> self-sanity check prior to filing a bug report:
>>
>> attempted replacement that generates an error leaves a '*tmp*'
>> variable in the global environment.
>>
>> test <- 1:10
>> test[2:4] <- expression(e)
>> ls()
>>
>> i've read section 3.4.4 of the "R Language Definition" which
>> discusses the mechanism for replacement, and it is not clear to me
>> whether this was intended, but i suspect not (to be honest, it's not
>> clear to me why the process as described doesn't generate an infinite
>> recursion -- perhaps the primitive treats the argument named '*tmp*'
>> different than other arguments). i've also searched the R site, and
>> can't find this particular issue discussed.
>>
>> even though, as below, i am using 2.4.0 alpha, this happens as well
>> in 2.3.1.
>>
>> from my standpoint, desirable behavior would be:
>>
>> (i) if an error occurs, remove the '*tmp*' variable
>
> That's a bug: it need a context set to clean up.
Fixed in 2.4.0
>> (ii) report the error as occurring in the original replacement call
>> (rather than the '*tmp*' replacement, which may be confusing to those
>> who haven't read the "R Language Definition")
>
> But by that point the call may have been transformed quite dramatically.
> I was going to suggest traceback() would give you a sensible call, but in
> this case it is not doing so: at a quick glance that is also due to no
> context being set.
That was true for some of the subassignment error messages, but not this
one: it depended on whether error() or errorcall() was used. Since it
potentially changes error messages in package checking, I have tidied this
up for 2.5.0 only.
> There is also the question as to whether this should have worked. It
> probably could be made to do so as
>
> test <- as.expression(test)
> test[2:4] <- expression(e)
Yes, this was just some missing cases in subassign.c which I have added
for 2.5.0. Here is a related case in R-devel:
> test <- 1:10
> try(test[2:4] <- ls) # fails
Error in test[2:4] <- ls : incompatible types (from closure to integer) in
subassignment type fix
Compare 2.4.0 beta:
> test <- 1:10
> try(test[2:4] <- ls) # fails
Error in `[<-`(`*tmp*`, 2:4, value = function (name, pos = -1, envir =
as.environment(pos), :
incompatible types (from closure to integer) in subassignment type
fix
--
Brian D. Ripley, [EMAIL PROTECTED]
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 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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