Variable/function namespaces WAS: Bug in subsetting data frame (PR#13515)

Stavros Macrakis wrote:
On Tue, Feb 10, 2009 at 8:31 AM, Duncan Murdoch <murdoch at stats.uwo.ca>wrote:
The evaluator recognizes the context of usage and will get the
function for a function call....
Can you point me to chapter and verse in the language definition...
No, I'm also unable to find it.
! This seems like a pretty fundamental thing to leave undocumented....
...I think originally there was no difference, and it caused the obvious trouble when people used variable names like t and c other short function names, so this was added.  I don't remember whether the different lookup rules showed up first in R or S.
There is an interesting discussion of these issues (in a Lisp context)
in "Technical Issues of Separation in Function Cells and Value Cells"
Lisp and Symbolic Computation 1:1:81 (6/1988) -- available at
http://www.nhplace.com/kent/Papers/Technical-Issues.html.  I don't
think an R-style approach is discussed there, though.

                -s
On Tue, Feb 10, 2009 at 10:11 AM, Duncan Murdoch <murdoch at stats.uwo.ca> wrote:
Stavros Macrakis wrote:
On Tue, Feb 10, 2009 at 8:31 AM, Duncan Murdoch <murdoch at stats.uwo.ca>wrote:
The evaluator recognizes the context of usage and will get the
function for a function call....
Can you point me to chapter and verse in the language definition...
No, I'm also unable to find it.
! This seems like a pretty fundamental thing to leave undocumented....
In open source nothing is undocumented, but sometimes the documentation 
is a little hard to read.  I think you want to look at the 
https://svn.r-project.org/R/trunk/src/main/eval.c section of the manual.

More seriously, I agree, but I don't have time to fix the omission.  If 
you work out a logical (from your point of view) place to put this, and 
write a first draft in texinfo format, I'll put it in.

Duncan Murdoch

...I think originally there was no difference, and it caused the obvious trouble when people used variable names like t and c other short function names, so this was added.  I don't remember whether the different lookup rules showed up first in R or S.
There is an interesting discussion of these issues (in a Lisp context)
in "Technical Issues of Separation in Function Cells and Value Cells"
Lisp and Symbolic Computation 1:1:81 (6/1988) -- available at
http://www.nhplace.com/kent/Papers/Technical-Issues.html.  I don't
think an R-style approach is discussed there, though.

                -s

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