On Thu, 17 May 2007, Seth Falcon wrote: > One of the things I find most problematic in R is the partial matching > of names in lists. Robert and I have discussed this and we believe > that having a mechanism that does not do partial matching would be of > significant benefit to R programmers. To that end, I have written a > patch that modifies the behavior of "[[" as follows: > > 1. [[ gains an 'exact' argument with default value NA > > 2. Behavior of 'exact' argument: > > exact=NA > partial matching is performed as usual, however, a warning > will be issued when a partial match occurs. This is the > default. > > exact=TRUE > no partial matching is performed. > > exact=FALSE > partial matching is allowed and no warning issued if it > occurs. > > This change has been discussed among R-core members and there appeared > to be a general consensus that this approach was a good way to > proceed. However, we are interested in other suggestions from the > broader R developer community. > > Some additional rationale for our approach: > > Lists are used as the underlying data structures in many R programs > and in these cases the named elements are not a fixed set of things > with a fixed set of names. For these programs, [[ will be used with > an argument that gets evaluated at runtime and partial matching here > is almost always a disaster. Furthermore, dealing with data that has > common prefixes happens often and is not an exceptional circumstance > (a precondition for partial matching issues).
This sounds interesting. Do you intend to leave the $ operator alone, so it will continue to do partial matching? I suspect that that is where the majority of partial matching for list names is done. It might be nice to have an option that made x$partial warn so we would fix code that relied on partial matching, but that is lower priority. ---------------------------------------------------------------------------- Bill Dunlap Insightful Corporation bill at insightful dot com 360-428-8146 "All statements in this message represent the opinions of the author and do not necessarily reflect Insightful Corporation policy or position." ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
