[Rd] conditionally import a namespace?

[Felix Andrews]

Dear R-devel,

I have a problem defining the dependencies for a package.

My package (latticist, not yet released) "Suggests" RGtk2, but
specifically does not require it. If RGtk2 is available, the user can
call a function that builds a GUI with RGtk2. However, I do not want
to attach the RGtk2 namespace, because it is irrelevant to the user
and exports about 7500 symbols.

Last time I asked a similar question to this, Professor Ripley noted
that the usual method to get around this situation is the use an
explicit package prefix to function calls (the `::` operator). But
this is not so easy with non-standard functions. Take this chunk of
code:

widg <- gtkComboBoxEntryNewText()
widg$show()
widg["width-request"] <- 100

The first call is easy to prefix, as RGtk2::gtkComboBoxEntryNewText()
but the others, `$.RGtkObject` and `[<-.RGtkObject` are not.

While I *could* rewrite all the code to use explicit functions, I
think, the resulting code would be much less clear.

Essentially what I want to do is conditionally import the RGtk2 namespace.

Any suggestions?

Thanks
Felix

-- 
Felix Andrews / 安福立
http://www.neurofractal.org/felix/
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