> On 5/8/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
> > [Alexander Stoddard]
> > > Subject: Re: [Rd] How to understand packages, namespaces,
> > > environments
> > >
> > > >
> > > > Does saying the following load package 'foo' into its own
> > > environment ?
> > > > > library(foo)
> > >
> > [Duncan Murdoch]
> > > This loads some of the (name, object) pairs from the package into
> > > two
> > > environments: the public one the user can see, and the namespace
> > > one that the code in the package can see. They're related, you
> > > don't get two copies of the objects.
> >
[MVB]
> > That's interesting-- I thought there really were two copies. In my
> > debug package, I've taken the approach of changing both copies.
>
[Gabor Grothendieck]
> How does one refer to the two different copies? Thanks.
>
>
The help for fun.locator (in the debug package) contains my
interpretation of what's going on (which might be wrong, but seems to
work). A slightly simplified version of the guts of fun.locator is as
follows:
# function to check for something called fname
is.here <- function( env) exists( fname, env=env, inherits=FALSE)
# Search path
search.envs <- lapply( 1:length( search()), pos.to.env)
ff <- search.envs[ sapply( search.envs, is.here)]
# Hidden namespace environments
ln <- lapply( loadedNamespaces(), asNamespace)
ff <- c( ff, ln[ sapply( ln, is.here)])
# S3 methods:
S3 <- lapply( ln, function( x) if( exists( '.__S3MethodsTable__.', x,
inherits=FALSE))
get( '.__S3MethodsTable__.', x) else 0)
S3 <- S3[ !sapply( S3, is.numeric)]
ff <- c( ff, S3[ sapply( S3, is.here)])
Then ff is a list of environments where a copy (?) of fname exists-- and
you can use
ff[[i]][[fname]]
or
get(fname, env=ff[[i]]) & assign( fname, ..., env=ff[[i]])
I should point out that the doco for asNamespace says "not intended to
be called directly"-- but I couldn't see an alternative, and anyway it
seems to work (for now).
Mark
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