[Rd] Proposing a change in the base::sink interface for type argument

[Kasper Daniel Hansen]

In other words: this is a standard programming paradigm in R/S which
(unfortunately) is not widely known, based on my network.  It is really
nice for developers.

Best,
Kasper

On Wed, Mar 18, 2015 at 5:42 PM, MacQueen, Don <macqueen1 at llnl.gov> wrote:

> It's only an illusion until one actually tries providing a vector.
>
>   > sink('foo', type=c('s','m'))
>   Error in match.arg(type) : 'arg' must be of length 1
>
> The additional benefit of match.arg() which you may have not appreciated
> is that it allows the user to abbreviate. That is,
>   > sink('foo', type='o')
> is valid usage. The essential concept of match.arg() is that it tries to
> match whatever the user supplied with one, and only one, of the values
> provided in the argument's default value, and that is the value used in
> the rest of the function.
>
> For example:
> > foo <- function(arg=c('aa','bb','cc')) cat(match.arg(arg),'\n')
> > foo('a')
> aa
> > foo('b')
> bb
> > foo('x')
> Error in match.arg(arg) : 'arg' should be one of "aa", "bb", "cc"
> >
> > foo('aa')
> aa
>
>
>
>
> Being "non-intuitive" or puzzling to people coming from other languages is
> not a sufficient reason for a change. Obviously, different languages have
> different features, otherwise, why bother to have different languages?
>
> And yes, match.arg() is widely used in R. I find it quite useful in my own
> programming.
>
>
> --
> Don MacQueen
>
> Lawrence Livermore National Laboratory
> 7000 East Ave., L-627
> Livermore, CA 94550
> 925-423-1062
>
>
>
>
>
> On 3/16/15, 10:08 PM, "Hamid Bazzaz" <hhamid at gmail.com> wrote:
>
> >Hi folks,
> >
> >Here is the current interface:
> >
> >sink(file=NULL, append=FALSE, type = c("output", "message"), split=FALSE)
> >
> >However, reading the implementation there is implicit assumption that type
> >is a single character value:
> >https://github.com/wch/r-source/blob/trunk/src/library/base/R/sink.R#L23
> >
> >I'm finding this very confusing as the interface is giving a default value
> >of a character _vector_ causing the illusion that by default both
> >output/message will be redirected.
> >
> >I'm proposing either a change in the interface so it is a single character
> >(either output or message) or a loop in the implementation on all values
> >in
> >type so it will actually be considered a vector. Here is an example change
> >for the former:
> >
> >
> https://github.com/hhamid/r-source/commit/d3cad22e1b9beca0a55004d74fc95059
> >c279d770#diff-498a99501a04c6d9a66ee95ad6614734L19
> >
> >Just wondering what people think and if this makes sense.
> >
> >Thanks a lot,
> >Hamid
> >
> >       [[alternative HTML version deleted]]
> >
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>
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