[R] Packages: What expressions are allowed outside/before .First.lib?

[Henrik Bengtsson]

Follow up on my own message: I found autoload(), see under Q4 below:

> -----Original Message-----
> From: owner-r-help at stat.math.ethz.ch
> [mailto:owner-r-help at stat.math.ethz.ch]On Behalf Of Henrik Bengtsson
> Sent: Tuesday, August 07, 2001 11:21 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Packages: What expressions are allowed outside/before
> .First.lib?
>
>
> Sorry for this long message. The two first questions asks for
> general coding
> standard when creating packages, the third one asks if the .R files are
> concatenated in lexical order or not, the fourth question is a "how-to"
> question. All questions are related. If there is a reference where I can
> read about this please tell me, because then I could repost a more
> restricted set of questions.
>
> Q1. When loading pakages, if exists, the .First.lib function will
> be called
> in the end. Is it correct that it is only in .First.lib one should have
> "executable" code? Is it also true that "outside" .First.lib,
> only function
> declarations and objects assignments such as '.conflicts.OK <-
> TRUE' should
> be used?
>
> Q2. Is it considered ok to use attr() outside .First.lib? I would like set
> an attribute 'modifiers' to all my functions as they are declared. I have
> tried it and it work. This is an example of how one of my
> generated package
> files looks like:
>
>   callMe0 <- function(x)
>     cat("hey\n")
>   attr(callMe0, "modifiers") <- c("private")
>
>   callMe <- function(x)
>     callMe0(x)
>   attr(callMe, "modifiers") <- c("public")
>
> I know that I could put the attr() assignments in the .First.lib function,
> but since I/we write code in (many) separated .R files, which are
> concatenated when the library is build, it would be doomed to miss one or
> have one to many. So, is the above code considered to be alright? (The
> 'private' and 'public' attributes are used to "hide" some of the functions
> from the end user.)
>
>
> Q3. After having used the attr() approach for a while, we wanted
> to add some
> control of the assignment of 'modifiers'. I wrote a function "modifiers<-"
> that assert that the values are valid before setting the
> attribute. Now the
> code would look like
>
>   callMe0 <- function(x)
>     cat("hey\n")
>   modifiers(callMe0) <- c("private")
>
>   callMe <- function(x)
>     callMe0(x)
>   modifiers(callMe) <- c("public")
>
> I think this code is a little bit more readable, but bullet-proof in the
> sence that unknown modifiers can not be set. But, by doing this I
> know I am
> in deep water; to load this library I rely on the fact that
> "modifiers<-" is
> already declared. It looks like the library source file is created by
> concatenation the .R files in lexical order and one can force the
> declaration of "modifiers<-" to appear first by putting it in a
> file called
> "000.R" (zeros). However, I don't know if one can rely on this?!
>
>
> Q4. What I really want to do is to declare "modifiers<-" in
> another package,
> lets call it, 'myrootlib', which all other libraries we write relies on.
> Trying
>
>   require(myrootlib)  # Declares "modifiers<-"
>
>   callMe0 <- function(x)
>     cat("hey\n")
>   modifiers(callMe0) <- c("private")
>
>   callMe <- function(x)
>     callMe0(x)
>   modifiers(callMe) <- c("public")
>
> won't work! The reason for this seems to be that the package
> 'myrootlib' is
> not loaded (evaluated) until afterwards. This brings up the
> issues asked in
> Q1 and Q2. Is there another way to do it or do we have to go back to the
> approaches explained in Q3, Q2 or even Q1?
>

Instead of 'require(myrootlib)' above, it looks like
'autoload("modifiers<-", "myrootlib")' would work. Is this a correct way to
use autoload?

> Thank you so much!
>
> Henrik Bengtsson
>
> Lund University/UC Berkeley
> hb at maths.lth.se
>
> PS. Any questions I ever ask about [R] and possible improvements
> for it, is
> to improve my (and hopefully others) understanding and never to
> complain. I
> appreciate all the work done by all the contributors and testers. Thanks.
> DS.

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._