[Rd] identical(..., ignore.environment=TRUE)

[William Dunlap]

MM> but I don't think we'd want to
MM> change  all.equal.language()  at this point in time

Although it would be nice if all.equal looked at least at attributes of
formulas
so we did not get results like
  > form <- y ~ x1 %in% x2
  > all.equal(form, terms(form))
  [1] TRUE
  > all.equal(terms(y~x1+x2+Error(x3/x2), specials="Error"),
terms(y~x1+x2+Error(x3/x2)))
  [1] TRUE



Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Tue, Oct 13, 2015 at 8:39 AM, Martin Maechler <maechler at stat.math.ethz.ch
> wrote:

> >>>>> Duncan Murdoch <murdoch.duncan at gmail.com>
> >>>>>     on Mon, 12 Oct 2015 19:31:11 -0400 writes:
>
>     > On 12/10/2015 9:51 AM, Ben Bolker wrote:
>     >> Duncan Murdoch <murdoch.duncan <at> gmail.com> writes:
>     >>
>     BB>
>     >>>>> It seems odd/inconvenient to me that the
>     >>>>> "ignore.environment" argument of identical() only
>     >>>>> applies to closures (which I read as 'functions' --
>     >>>>> someone can enlighten me about the technical
>     >>>>> differences between functions and closures if they
>     >>>>> like -- see below for consequences of my confusion).
>     >>>>> This is certainly not a bug, it's clearly documented,
>     >>>>> but it seems like a design flaw.  It would certainly
>     >>>>> be convenient to be able to ignore differences in
>     >>>>> environments when comparing complex objects with lots
>     >>>>> of deeply nested formula and terms objects with
>     >>>>> environments ...
>     >>>>>
>     >>>>> Can anyone suggest a reason for this design?
>     >>>>>
>     >>
>     >> [snip]
>     >>
>     >>>>> Actually, maybe I don't understand how this is
>     >>>>> supposed to work since I thought this would be TRUE:
>     >>>>>
> >>>>> f1 <- function() {}
> >>>>> f2 <- function() {}
> >>>>> environment(f1) <- new.env()
> >>>>> environment(f2) <- new.env()
> >>>>> identical(f1,f2,ignore.environment=TRUE) ## FALSE
>     >>>>
>     >>>> Those two functions likely have different srcref
>     >>>> attributes.  If you created f2 using f2 <- f1, you'd
>     >>>> get your expected result.
>     >>>>
>     >>
>     >> [snip]
>     >>
>     >> Thanks for the clarification about closures
>     >> vs. functions.
>     >>
>     >> [snip]
>     >>
>     >> You're right that the srcref attributes are different;
>     >> although their bodies are the same, they have their own
>     >> environments that differ.  For me, this makes the
>     >> intended use of ignore.environment= even more puzzling;
>     >> given that environments are not ignored recursively
>     >> (that's not exactly what I mean -- I mean ignoring all
>     >> environments of components of an object), I have trouble
>     >> understanding the use case for ignore.environnment ...
>     >> maybe it was developed before srcrefs existed?
>
>     > I think it simply means "ignore.environment.of.closures",
>     > as the description says, but that's too long to be a
>     > convenient arg name.
>
>     > Closures have three parts: the formals, the body and the
>     > environment.  (Actually, 4 parts: like almost all R
>     > objects, they may also have attributes.)
>
>     > That arg just says to ignore the environment part when
>     > comparing closures.  It doesn't say to ignore environments
>     > in general.
>
> For another beat on a dead horse, @ Ben:
>
> You could either use  options(keep.source = FALSE) in your
> enviroment such that your functions should not have any 'srcref'
> attributes anymore,
>
> or probably more sensible, use
>
> all.equal(f1, f2) rather than identical(f1, f2, ..)
>
> which I think should really do what you want
> [even though it ends up using string comparison after deparse(.)
>  .. about which one can debate... but I don't think we'd want to
>  change  all.equal.language()  at this point in time].
>
> Martin
>
>
>     >>
>     >> In the R code base it's used in checkConflicts (to see if
>     >> a function is re-exported) and in getAnywhere ...
>     >>
>
>     > I'd say those uses are slightly bogus.  You should
>     > generally remember that closures have 3 (or 4) parts, and
>     > not go around comparing only two (or 3) of them.
>
>     > Duncan Murdoch
>
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