Perhaps it should have another name, be made generic and extended to functions in which case it would work on the formal arguments. e.g.
read.table.comma <- modify(read.table, list(sep = ",")) would return a function that is the same as read.table but has "," as the default for sep. Python has something like this called partial: http://docs.python.org/dev/whatsnew/pep-309.html On 9/18/06, Deepayan Sarkar <[EMAIL PROTECTED]> wrote: > On 9/15/06, Deepayan Sarkar <[EMAIL PROTECTED]> wrote: > > On 9/15/06, Martin Maechler <[EMAIL PROTECTED]> wrote: > > > >>>>> "DeepS" == Deepayan Sarkar <[EMAIL PROTECTED]> > > > >>>>> on Fri, 15 Sep 2006 12:22:15 -0700 writes: > > > > > > DeepS> Hi, since lattice uses nested lists in various > > > DeepS> situations, it has had an unexported function called > > > DeepS> updateList for a while, which looks like > > > > > > >> > lattice:::updateList > > > >> function (x, val) > > > >> { > > > >> if (is.null(x)) > > > >> x <- list() > > > >> if (!is.list(x)) > > > >> stop("x must be NULL or a list") > > > >> if (!is.list(val)) > > > >> stop("val must be a list") > > > >> xnames <- names(x) > > > >> for (v in names(val)) { > > > >> existing <- v %in% xnames > > > >> if (existing && is.list(x[[v]]) && is.list(val[[v]])) > > > >> x[[v]] <- updateList(x[[v]], val[[v]]) > > > >> else x[[v]] <- val[[v]] > > > >> } > > > >> x > > > >> } > > > > > > [I'm not sure I'd allow NULL for 'x'; typing list() instead of > > > NULL is not much more, but when the function name even includes 'list' > > > I'd really require a list for 'x'] > > > > Makes sense. > > > > > You could hence collapse the first 6 lines to the single > > > > > > stopifnot(is.list(x), is.list(val)) > > > > I'll check if lattice needs some fixes with this. > > Actually, I do need to allow NULL, because update.trellis does things like > > update.trellis <- function(object, ..., par.strip.text, ...) > { > ... > object$par.strip.text <- updateList(object$par.strip.text, par.strip.text) > ... > } > > where object$par.strip.text may be initially NULL. But I'll do that > inside a lattice wrapper. > > > > DeepS> Basically, it recursively replaces elements that have > > > DeepS> been specified in val, leaving the other components > > > DeepS> alone. I'm not aware of any other actual situation > > > DeepS> where this is useful, but it certainly can be, so I > > > DeepS> want to export this functionaliy. At least one other > > > DeepS> person (Gabor) has also asked for that. > > > > > > I've had a similar need only recently: > > > If a list is used to store "defaults" and you want a safe way to > > > change only a few of the values... > > > I presume you use this for manipulating the settings of lattice > > > parts ? > > > > Yes, it's primarily used inside trellis.par.set, but many other places as > > well. > > > > > DeepS> Now, as the name suggests, I think it might be > > > DeepS> reasonable to export this as an update method for > > > DeepS> "list" objects. Depending on what others (in > > > DeepS> particular r-core) think, one of these things might > > > DeepS> happen: > > > > > > DeepS> (1) I export it as updateList (or some other name) in lattice > > > DeepS> (2) I export it as an S3 method update.list in lattice > > > DeepS> (3) It gets added as an S3 method update.list in one of the > > > base packages > > > or > > > (4) it gets added as utility function updateList() to > > > 'utils' {= one of the base packages} > > > > Yes, that a good option too (certainly better than (1)) > > > > > which I'd favor momentarily. > > > - update() is typically for updating *models* > > > - it's not clear that this is *the* method for update()ing a list > > > > I agree. Part of the reason I brought this up is because it is not > > clear to me what justifies a new method for an existing generic. An > > argument for is that one doesn't introduce yet another function, which > > (I thought) might be enough if the other choice is to not have any > > method at all. > > > > > I'm also a bit wondering if it wouldn't make sense to change the name to > > > something like assignInList(). > > > > I'm open to suggestions for the name. I didn't think too much about it > > since it was unexported anyway. > > > > > DeepS> The default option is (1), and I guess Sept 19 is the deadline > > > for any > > > DeepS> of these to be included in R 2.4.0. > > > > > > Yes, that's true for (3) & (4) are higher if you provide a patch > > > to R-devel (not R-alpha) which includes a man page ... [but > > > don't hurry, I'd like to see other comments] > > I have checked in > > https://svn.r-project.org/R-packages/trunk/lattice/R/modifyList.R > https://svn.r-project.org/R-packages/trunk/lattice/man/modifyList.Rd > > which I'm happy to offer for inclusion in utils or wherever might seem > appropriate. I'll upload a version of lattice which includes these > late tomorrow if I don't see any more comments by then. > > I've changed the name because I wasn't sure if assignInList might be > confusing, as the semantics are different from those of assign (assign > is like 'fix', while this is more like 'edit'). However, any name is > fine with me. > > Deepayan > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
