[Rd] switch() disallowing multiple default values Re: Bug in parseNamespaceFile or switch( , ... ) ?

[Prof Brian Ripley]

On Sun, 28 Nov 2010, Duncan Murdoch wrote:

> I've now committed changes in R-devel and R-patched to detect cases where a 
> call to switch() contains multiple unnamed alternatives.  The code only 
> complains if the EXPR argument is a character string; unnamed alternatives 
> are fine with numeric switching.
>
> Adding this check turned up 3 more typos like this in the base code besides 
> the one in parseNamespaceFile.  I expect it will turn up quite a few more in 
> CRAN and Bioconductor packages.
>
> Please let me know right away if you've got correct code that generates the 
> warnings or errors.

Most of the errors seem to be of the form (here from Brobdingnag)

                    trunc  = callGeneric(as.complex(x)),,,

that is, empty arguments to switch.

>
> Duncan Murdoch
>
>
>  In R-devel they're an error, in R-patched they'll just give a warning.
>
> On 27/11/2010 7:09 PM, Duncan Murdoch wrote:
>> On 27/11/2010 6:50 PM, Duncan Murdoch wrote:
>>> On 27/11/2010 5:58 PM, Charles C. Berry wrote:
>>>> 
>>>> parseNamespaceFile() doesn't seem to detect misspelled directives. 
>>>> Looking
>>>> at its code I see
>>>>
>>>>     	switch(as.character(e[[1L]]),
>>>>
>>>>     	<lots of args omitted here>,
>>>>
>>>>     	stop(gettextf("unknown namespace directive: %s",
>>>>                     deparse(e)), call. = FALSE, domain = NA))
>>>> 
>>>> but this doesn't seem to function as I expect, viz. to stop with an error
>>>> if I type a wrong directive.
>>> 
>>> You're right, there was a typo in parseNamespaceFile.  (The typo was in
>>> this line:
>>>
>>>                   "=", "<-" = {
>>> 
>>> This should have been
>>>
>>>                   "=" =, "<-" = {
>>> 
>>> Without the extra = sign, the "=" was taken as the default value of the
>>> switch, and the stop() was never reached.
>>> 
>>> Conceivably switch() should complain if it is called with more than one
>>> default.
>> 
>> I suspect when I fix this it's going to flush out some typos in packages
>> on CRAN...
>> 
>> Duncan Murdoch
>> 
>> 
>>> Duncan Murdoch
>>> 
>>>> 
>>>> Details:
>>>>> # create dummy NAMESPACE file with two bad / one good directives
>>>>> cat("blah( nada )\nblee( nil )\nexport( outDS )\n",file="NAMESPACE")
>>>>> readLines("NAMESPACE")
>>>> [1] "blah( nada )"    "blee( nil )"     "export( outDS )"
>>>>> parseNamespaceFile("",".") # now parse it
>>>> $imports
>>>> list()
>>>> 
>>>> $exports
>>>> [1] "outDS"
>>>> 
>>>> $exportPatterns
>>>> character(0)
>>>> 
>>>> $importClasses
>>>> list()
>>>> 
>>>> $importMethods
>>>> list()
>>>> 
>>>> $exportClasses
>>>> character(0)
>>>> 
>>>> $exportMethods
>>>> character(0)
>>>> 
>>>> $exportClassPatterns
>>>> character(0)
>>>> 
>>>> $dynlibs
>>>> character(0)
>>>> 
>>>> $nativeRoutines
>>>> list()
>>>> 
>>>> $S3methods
>>>>          [,1] [,2] [,3]
>>>> 
>>>>> 
>>>> 
>>>> So, it picked up 'export' and ignored the other two lines.
>>>> 
>>>> 
>>>> Chuck
>>>> 
>>>> p.s.
>>>> 
>>>>> sessionInfo()
>>>> R version 2.12.0 (2010-10-15)
>>>> Platform: i386-apple-darwin9.8.0/i386 (32-bit)
>>>> 
>>>> locale:
>>>> [1] C
>>>> 
>>>> attached base packages:
>>>> [1] stats     graphics  grDevices utils     datasets  methods   base
>>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> Charles C. Berry                            Dept of Family/Preventive 
>>>> Medicine
>>>> cberry at tajo.ucsd.edu			    UC San Diego
>>>> http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 
>>>> 92093-0901
>>>> 
>>>> ______________________________________________
>>>> R-devel at r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>> 
>> 
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

-- 
Brian D. Ripley,                  ripley at 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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595