From pgilbert at bank-banque-canada.ca  Tue Aug 29 20:24:27 2006
From: pgilbert at bank-banque-canada.ca (Paul Gilbert)
Date: Tue, 29 Aug 2006 14:24:27 -0400
Subject: [Rd] 'CanMakeUseOf' field
In-Reply-To: <m28xl7ctt3.fsf@ziti.fhcrc.org>
References: <m2wt8sgyo0.fsf@ziti.fhcrc.org>	<17651.65163.240840.365787@stat.math.ethz.ch>	<44F4473D.9030203@bank-banque-canada.ca>	<17652.19292.998960.686119@stat.math.ethz.ch>	<44F46112.7060809@stats.uwo.ca>
	<m2d5ajedon.fsf@ziti.fhcrc.org>	<44F47295.2050207@stats.uwo.ca>
	<m28xl7ctt3.fsf@ziti.fhcrc.org>
Message-ID: <44F4865B.5010107@bank-banque-canada.ca>

Seth Falcon wrote:

>Duncan Murdoch <murdoch at stats.uwo.ca> writes:
>  
>
>>On 8/29/2006 11:58 AM, Seth Falcon wrote:
>>    
>>
>>>I think there is an important distinction between a dependency needed
>>>for the package to function and a dependency needed to demonstrate
>>>said functionality via an example or vignette.  The former is what
>>>Depends is about, the latter is something else (Suggests).
>>>      
>>>
>>Yes, that's a good point, especially with vignettes.  Only the package
>>author needs to be able to run them.
>>    
>>
>
>Yes, but just to keep things clear: the value of vignettes is that
>users can follow along.  So the ability to programatically identify
>the extra required packages is valuable.
>
>  
>
>>But maybe examples should be considered broken if they don't
>>work. Users should be able to expect example(foo) not to generate an
>>error.  Package authors should wrap optional examples in code like if
>>(require(...)).
>>    
>>
This is a work around that is ok for the developer's testing and to 
prevent failure on CRAN, and I use it. But, other than actually reading 
the examples, it provides no hints to other testers or users about 
things that might be installed, or installed first, to give more 
complete testing and more functionality.

Looking toward the future, I think it would be useful to have a standard 
mechanism to indicate extensions that are available in a package, and 
might be tested and used, but are not necessarily available on CRAN. For 
instance, an example might access to a purchased database or take 
advantage of  a computer cluster. It seems limiting to think that all 
testing that cannot be done on CRAN must be done almost exclusively by 
the developer.

Paul

>
>I agree.  As with vignettes, there is value in users being able to
>follow along and it would be nice to have a programatic way to
>identify extra package needed for fancy/involved/optional examples.
>
>Best,
>
>+ seth
>
>______________________________________________
>R-devel at r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-devel
>  
>
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[Rd] 'CanMakeUseOf' field
Paul Gilbert