Darwinian software development and the library function
Hi Spencer, Sorry, I wasn't very clear in my initial post. The function print.foo (myfoo, ...) won't pass R check (unless one overwrites print first). One has to write print.foo (x, ...), which in my personal opinion, can be problematic. In my oosp package, I have overwritten print (along with a few others). Initially, I overwrote both print and print.default. However now, I merely use print = function (...) base::print (...). Not really a generic, however it acts exactly the same (I think...). Plus Rd documentation still documents print.mymethod in the usual way. kind regards Charlotte
On Sat, Feb 13, 2010 at 4:41 AM, spencerg <spencer.graves at prodsyse.com> wrote:
Hi, Charlotte: ? ? I'm not sure what you mean. ?If you mean writing something like "print.foo (myfoo, ...)", this is relatively benign I suppose, but I avoid it where feasible. ?On multiple occasions, I've pushed collaborators and even maintainers of other packages to change this or allow me to change it to conform to the standard; ?if my memory is correct, there have been several violations of this standard in the "fda" package, which are no longer there because I changed them. ?If a user with an object "x" of class "foo" writes print(x=x) or print(foo=x), I'm not sure what it would do, but it might not be what you want. ? ? My "sos" package masks "?". ?However, I don't like it. ?I generally consider such to be potentially user hostile, and whenever feasible, I prefer to avoid such code. ?I did it in this case for a couple of reasons. ?First, using "?" (actually "???") seems so much easier to remember than "findFn" that it justifies this transgression of standard protocol. ?Second, one of the leading figures in the R community (Duncan Murdoch) contributed suggested we do this and contributed the code. ? ? If you change the definition of "print" itself, that seems to me to be a much bigger issue, with consequences much more difficult to predict. ?If someone else also overwrites "print" making it different and incompatible with yours, then your code may not work or theirs may not, depending on which gets loaded first in the search path. ?Worse, your code cannot possibly have been tested as thoroughly as the standard code. ?If your code includes a subtle bug that only occurs under special circumstances, it may be hard for the person experiencing the problem to find, because they don't expect it. ? ? Hope this helps. ? ? Spencer Charlotte Maia wrote:
Hi all, Legend has it, that polite R programmers don't overwrite, say, the print function. However, this seems quite un-Darwinian to me (especially given that I don't want to call all my arguments x and y). I might want a function print.foo (myfoo, ...). So I decided to be very impolite (in one of my packages) and overwrite a few standard generics. Plus, to the best of my knowledge it doesn't interfere with normal use (yay...). This brings us to the library function. Which by default gives a whole lot of warnings loading my package (and any other package that does something similar), scaring off polite R programmers and perhaps some mainstream R users. I'm starting to think that the default for library, should be warn.conflicts=FALSE. However, just reading the documentation, I noticed a reference to something called .conflicts.OK. Not sure what that does, however if it does what it sounds like, then it largely fixes the problem. The biggest issue though, is whether or not one should be impolite (i.e. Darwinian) and overwrite print etc in the first place...? I'm inclined to go in favour of overwriting the functions. However, it has the potential to introduce some technical problems. Other's opinions appreciated. kind regards
-- Spencer Graves, PE, PhD President and Chief Operating Officer Structure Inspection and Monitoring, Inc. 751 Emerson Ct. San Jos?, CA 95126 ph: ?408-655-4567
Charlotte Maia http://sites.google.com/site/maiagx