On 21/07/2018 10:54 PM, Aaron Jacobs wrote:
Excuse me if this is inappropriate content for this list, but I thought it
might be the best place -- and the best audience -- to ask about a design
decision for the R language.
Programs or analyses written in R typically use library() to pull in
functions from non-core packages. This differs markedly from most
languages*, which usually offer some way to selectively import symbols. For
example, in Python you'd see "from random import randint", and so on.
I think there are two reasons. First, the :: operator is so convenient.
If you really wanted "from random import randint" you could write
randint <- random::randint
but most people don't bother with the assignment, preferring to just
work with random::randint in their code.
The second reason is that R encourages complex programs to be written as
packages, which do have the importFrom() directive. If you've got great
big scripts where you would want to import certain functions and don't
want the overhead of the package:: prefix, you're doing it wrong.
Duncan Murdoch
Within R packages, the NAMESPACE file provides this exact functionality
with the importFrom() directive, but the R language itself does not expose
this as a function for regular users.
I know that R did not have namespaces for some of its early existence, but
I'm curious as to why the language never acquired an import() or
importFrom() replacement for library() when it did get them. Was it purely
for compatibility with S and earlier R versions? Or was there a principled
difference of opinion on how R code should be written at stake?
Any insight from those of you familiar with R's history would be deeply
appreciated.
Regards,
Aaron
ps. I am aware of the very clever "import" package, which provides exactly
this feature -- I am more wondering why such an approach was never adopted
by the language itself.
* Most languages with real modules/namespaces, I mean.
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