Some of the uses of non-standard evaluation are undoubtedly a problem in
R. Probably the worst is in model.frame, because it is much harder to
work around. I have never used subset(,select=) and hence have never
been at risk of confusion (if you don't like how it works, I suggest you
do the same), but model.frame() is inside lots of things.
There are two issues here that I think are worth pointing out:
1/ Some things are just not fixable any more. They can only be fixed in a
new language. The people thinking about new statistical languages mostly
know what the problems are, because they have been using S and/or R for
many years and it's really not that hard to notice the problems. The
document on non-standard evaluation demonstrates that R-core is aware of
this particular problem.
2/ There are some uses of non-standard evaluation that don't seem to
confuse people, and an interesting question is how to characterise them.
These are what I referred to as 'macro-like functions' in the document
that you have already been referred to. For example, subset(,subset=) and
with() don't seem to be as confusing or to cause problems for programmers
in the same way. There is an empirical question as to what these
relatively non-problematic constructs are, and a theoretical question as
to why they are different. In particular, with() not only has non-standard
evaluation, it is quite similar to the notoriously confusing attach().
-thomas
On Tue, 11 Nov 2008, Wacek Kusnierczyk wrote:
Berwin A Turlach wrote:
On Tue, 11 Nov 2008 09:27:41 +0100
Wacek Kusnierczyk <[EMAIL PROTECTED]> wrote:
but then it might be worth asking whether carrying on with misdesign
for backward compatibility outbalances guaranteed crashes in future
users' programs, [...]
Why is it worth asking this if nobody else asks it?
i guess most of the people who do ask questions here care little about r
itself, they just want it to solve a problem, even if it involves
hacking the language.
those outside the r team who care about language design have probably
left the list long ago, if only they were subscribed. the fact that
it's only me asking is no statistics. i do talk to people, and know
many who'd ask, but they just don't care, because they have already
trashed r. instead of discouraging me, make use of that i care to ask.
vQ
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