[R] assign / environment side effect on R 2.4.0

[Thomas Petzoldt]

Hello,

I got several off-list answers to my question on R-Help:

"[R] list of interdependent functions" from  2006-06-20

and by evaluating this (and also my own example) I found differences in
the behavior of older versions of R (R 2.2.1 and 2.3.1) and the most
recent R 2.4. under development (SVN revision 38399, WinXP SP 2).

The example is a constructed cut-down  example, but this behavior is
observed also in different versions of the full implementation.

While in the older versions the environment of L$test remains
R_Globalenv, a changed environment is returned under R 2.4.0

Ist this side effect a "bug" or a "feature"? The list(unlist(L))
workaround helps to avoid the side effect.

Thomas




envfun <- function(L) {
  # L <- as.list(unlist(L)) # !!! workaround
  p <- parent.frame()
  assign("test", L$test, p)
  environment(p[["test"]]) <- p
}


solver <- function(L) {
  envfun(L)
  # some other stuff
}

L <- list(test = function() 1 + 2)

e1 <- environment(L$test)
solver(L)
e2 <- environment(L$test)

print(e1)
# <environment: R_GlobalEnv>

print(e2)
# <environment: 0x01d0b088>


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Thomas Petzoldt                    Tel. +49-351-463 3 4954
Technische Universitaet Dresden    Fax  +49-351-463 3 7108
Institut fuer Hydrobiologie        thomas.petzoldt at tu-dresden.de
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GERMANY

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