R devel - Feb 2000 - Something strange in "?assign"? (PR#433)

According to the assign helpfile (0.90.1) the "assign" function is

function (x, value, pos = -1, envir = sys.frame(sys.parent()),
  inherits = FALSE, immediate = TRUE)

which is not quite the implementation, which is

function (x, value, pos = -1, envir = pos.to.env(pos), inherits = FALSE, 
  immediate = TRUE)

This seems to have the following interesting effect.

"short.fun" <- function() {make(); ls()}
"make" <- function() assign("x", 3, envir =
sys.frame(sys.parent()))

short.fun()	# gives an x as I would expect

"make" <- function() assign("x", 3)

short.fun()	# now there's nothing here!

But since I have simply duplicated the default value, according to the
help file, I would expect these two "make" functions to behave
identically.  Is this to be expected, and if not, is this because the
definition of "assign" is slightly different to that in the help file?

Many thanks, Jonathan.

Jonathan Rougier                       Science Laboratories
Department of Mathematical Sciences    South Road
University of Durham                   Durham DH1 3LE
http://www.maths.dur.ac.uk/stats/people/jcr/jcr.html


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J.C.Rougier@durham.ac.uk writes:
> According to the assign helpfile (0.90.1) the "assign" function
is
> 
> function (x, value, pos = -1, envir = sys.frame(sys.parent()),
>   inherits = FALSE, immediate = TRUE)
> 
> which is not quite the implementation, which is
> 
> function (x, value, pos = -1, envir = pos.to.env(pos), inherits = FALSE, 
>   immediate = TRUE)
OK, that's a bug, in the documentation.

However, it is not a bug that sys.frame(sys.parent()) gives different
results as a default argument and as a supplied one. One is evaluated
in the function, the other in the caller!
> "short.fun" <- function() {make(); ls()}
> "make" <- function() assign("x", 3, envir =
sys.frame(sys.parent()))
> 
> short.fun()	# gives an x as I would expect
> 
> "make" <- function() assign("x", 3)
> 
> short.fun()	# now there's nothing here!
Try changing make() to function() {assign("x", 3);print(ls())}

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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