[R] functional (?) programming in r

Stavros Macrakis macrakis at alum.mit.edu
Tue Nov 18 04:44:47 CET 2008

On Mon, Nov 17, 2008 at 7:33 PM, Wacek Kusnierczyk
<Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
> Gabor Grothendieck wrote:
>> The R Language Definition manual that comes with R has a section on promises.


> on promises yes, but the question was whether the behaviour discussed
> before is obvious and intended, or unforeseen....


> ...what i would (r-naively) expect is that lapply for-loops over an index variable, and each promise picks from the list a value at that index....

Agreed. In fact, the man page for 'for' seems to explicitly specify
that the iteration variable is not mutable: "The variable var... is
read-only".  However, the implementation doesn't seem to enforce this:

      for (i in 1:5) print(i<-i)         # no error given for this assignment


More information about the R-help mailing list