[Rd] Request: Suggestions for "good teaching" packages, esp. with C code
ggrothendieck at gmail.com
Tue Feb 15 20:38:11 CET 2011
On Tue, Feb 15, 2011 at 1:04 PM, Paul Johnson <pauljohn32 at gmail.com> wrote:
> I am looking for CRAN packages that don't teach bad habits. Can I
> have suggestions?
> I don't mean the recommended packages that come with R, I mean the
> contributed ones. I've been sampling a lot of examples and am
> surprised that many ignore seemingly agreed-upon principles of R
> coding. In r-devel, almost everyone seems to support the "functional
> programming" theme in Chambers's book on Software For Data Analysis,
> but when I go look at randomly selected packages, programmers don't
> follow that advice.
> In particular:
> 1. Functions must avoid "mystery variables from nowhere."
> Consider a function's code, it should not be necessary to say "what's
> variable X?" and go hunting in the commands that lead up to the
> function call. If X is used in the function, it should be in a named
> argument, or extracted from one of the named arguments. People who
> rely on variables floating around in the user's environment are
> creating hard-to-find bugs.
> 2. We don't want functions with indirect effects (no <<- ), almost always.
> 3. Code should be vectorized where possible, C style for loops over
> vector members should be avoided.
> 4. We don't want gratuitous use of "return" at the end of functions.
> Why do people still do that?
> 5. Neatness counts. Code should look nice! Check out how beautiful
> the functions in MASS look! I want code with spaces and " <- " rather
> than everything jammed together with "=".
> I don't mean to criticize any particular person's code in raising this
> point. For teaching exemples, where to focus?
> Here's one candidate I've found:
> MNP. as far as I can tell, it meets the first 4 requirements. And it
> has some very clear C code with it as well. I'm only hesitant there
> because I'm not entirely sure that a package's C code should introduce
> its own functions for handling vectors and matrices, when some general
> purpose library might be more desirable. But that's a small point,
> and clarity and completeness counts a great deal in my opinion.
There was some discussion of this on stats stackexchange
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