If in my package "Foo" I call a function from another package "Bar" if it's
available, according to R-exts, this sounds like I should include "Suggests:
Bar" in package Foo's description. But the manual is silent on how to treat
Bar's namespace. Should I import it? If so, should this be conditional or
unconditional? There is a thread from 2008 in which Duncan Murdoch suggests
trying conditionally importing a package if it's installed, with the caveat "If
this is allowed" (http://tolstoy.newcastle.edu.au/R/e5/devel/08/10/0488.html).
This appears to work in current release of R, 2.15.2, but I'm still not clear
if it's officially allowed, much less recommended.
The manual also says:
> If a package only needs a few objects from another package it can use a fully
> qualified variable reference in the code instead of a formal import. A fully
> qualified reference to the function f in package foo is of the form foo::f.
> This is slightly less efficient than a formal import and also loses the
> advantage of recording all dependencies in the NAMESPACE file, so this
> approach is usually not recommended. Evaluating foo::f will cause package foo
> to be loaded, but not attached, if it was not loaded already—this can be an
> advantage in delaying the loading of a rarely used package.
>
Would this be a better solution than importing when calling into a suggested
package?
Davor
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