Hello,
first of all, thanks to LT for \pkg{codeutils}. I agree that it is
indeed very useful to identify errors and also to encourage re-thinking
past solutions. My problem:
I want to compare different sets of related sub-functions which should
be used alternatively by the same top-level function. Sets of related
functions should be bound together (as lists) and the workspace should
be as clean as possible.
Finally, these functions are to be called by top-level functions that
work with such sets.
What's the best way to do this?
- clutter the workspace with lots of functions?
OR:
- ignore "notes about possible problems"
OR:
- a third way?
Thanks in advance
Thomas P.
An example:
##=============================================================
## 1) One possible "set of functions"
flistA <- list(
foo = function() {
1:10
},
bar = function() {
log(foo())
}
)
## .. we may also have alternative sets,
## e.g. flistB, flistC, ... etc
## 2) Now we try to construct closures
## 2a) non-nested
makefun1 <- function(flist) {
with(flist,
function() foo()
)
}
## 2b) nested call
makefun2 <- function(flist) {
with(flist,
function() bar()
)
}
## 2c) or use an alternative way with a special function
## addtoenv, suggested by Gabor Grothendieck some times ago:
addtoenv <- function(L, p = parent.frame()) {
for(nm in names(L)) {
assign(nm, L[[nm]], p)
environment(p[[nm]]) <- p
}
L
}
makefun3 <- function(flist) {
addtoenv(flist)
function() bar()
}
## 3) now we create the "top-level" functions
## with one particular "set of functions"
m1 <- makefun1(flistA)
m2 <- makefun2(flistA)
m3 <- makefun3(flistA)
m1()
## this was no problem, trivial
m2()
# Error in bar() : could not find function "foo"
m3()
# works, but even in that case we get problems
# if we do this in a package:
# * checking R code for possible problems ... NOTE
# bar: no visible global function definition for 'foo'
## tested with R version 2.6.1 and
## R 2.7.0 Under development, svn rev. 44061
--
Thomas Petzoldt
Technische Universitaet Dresden
Institut fuer Hydrobiologie
01062 Dresden
GERMANY
http://tu-dresden.de/Members/thomas.petzoldt
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