[Rd] all.equal applied to function closures

[Martin Maechler]

>>>>> Bill Dunlap 
>>>>>     on Mon, 30 Nov 2020 13:41:54 -0800 writes:

    > To make the comparison more complete, all.equal.environment could compare
    > the parents of the target and current environments.  That would have to be
    > recursive but could stop at the first 'top level environment' (the global,
    > empty, or a package-related environment generally) and use identical
    > there.  E.g.,

    > > f1 <- function(x) (function(){ expx <- exp(x) ; function(y) y + expx})()
    > > all.equal(f1(2), f1(3))
    > [1] "Environments: Component “expx”: Mean relative difference: 1.718282"
    > 
    > [2] "Environments: <parent.env> Component “x”: Mean relative difference:
    > 0.5"

    > This is from the following, where I avoided putting the existing
    > non-recursive all.equal.environment into the body of this one.

    > all.equal.environment <-
    > function(target, current, ...)
    > {
    >     .all.equal.environment <- base::all.equal.environment # temporary hack
    >     stopifnot(is.environment(target), is.environment(current))
    >     if (identical(target, current)) {
    >         TRUE
    >     } else {
    >         msg <- NULL # TODO: check attributes
    >         # deal with emptyenv now since parent.env(emptyenv()) gives error
    >         # and topenv(emptyenv()) gives GlobalEnv
    >         eTarget <- identical(target, emptyenv()) ||
    > identical(target,topenv(target))
    >         eCurrent <- identical(current, emptyenv()) ||
    > identical(current,topenv(current))
    >         if (eTarget || eCurrent) {
    >             msg <- c(msg, paste("target is", format(target), "and current
    > is", format(current)))
    >         } else {
    >             thisComparison <- .all.equal.environment(target, current, ...)
    >             if (!isTRUE(thisComparison)) {
    >                 msg <- c(msg, thisComparison)
    >             }
    >             parentComparison <- Recall(parent.env(target),
    > parent.env(current), ...)
    >             if (!isTRUE(parentComparison)) {
    >                 msg <- c(msg, paste("<parent.env>", parentComparison))
    >             }
    >         }
    >         if (is.null(msg) || isTRUE(msg)) TRUE else msg
    >     }
    > }

Thank you, Duncan and Bill (and Kevin for bringing up the
topic).

I agree  all.equal() should work better with functions,

and I think probably it would make sense to define  all.equal.function()
rather than put this into all.equal.default()

However, it's not quite clear if it is always desirable to check the
environments as well notably as that *is* done recursively.

Bill, I'm sure you've noticed that we did write  all.equal.environment()
to work recursively... Actually, I had worked quite a bit at
that, too long ago to remember details, but the relevant svn log
entry is
------------------------------------------------------------------------
r66640 | maechler | 2014-09-18 22:10:20 +0200 (Thu, 18 Sep 2014) | 1 line

more sophisticated all.equal.environment(): no longer "simple" infinite recursions
------------------------------------------------------------------------

Are you sure that code with the internal recursive do1()
function should/could not be amended where needed?

Martin

    > On Mon, Nov 30, 2020 at 10:42 AM Duncan Murdoch <murdoch.duncan using gmail.com>
    > wrote:
    > 
    > > On 30/11/2020 1:05 p.m., Kevin Van Horn via R-devel wrote:
    > > > Consider the following code:
    > > >
    > > >      f <- function(x)function(y){x+y}
    > > >      all.equal(f(5), f(0))
    > > >
    > > > This returns TRUE, when it should return FALSE; I think it’s hard to
    > > make the case that f(5) and f(0) are “approximately equal” in any
    > > meaningful sense. Digging into the code for all.equal(), I see that
    > > all.equal(f(5), f(0)) results in a call to all.equal.language(f(5), f(0)),
    > > which only compares the function texts for equality.
    > > >
    > > > If it is decided to leave this behavior as-is, then at least it should
    > > be documented. Currently I cannot find any documentation for all.equal
    > > applied to functions.
    > >
    > > Clearly it should also compare the environments of the two functions,
    > > then it would see a difference:
    > >
    > >  > all.equal(environment(f(5)), environment(f(0)))
    > > [1] "Component “x”: Mean relative difference: 1"
    > >
    > > Changing the first few lines from
    > >
    > >      if (is.language(target) || is.function(target))
    > >          return(all.equal.language(target, current, ...))
    > >
    > > to
    > >
    > >      if (is.function(target)) {
    > >          msg <- all.equal.language(target, current, ...)
    > >          if (isTRUE(msg)) {
    > >              msg <- all.equal.environment(environment(target),
    > > environment(current), ...)
    > >              if (is.character(msg))
    > >                msg <- paste("Environments:", msg)
    > >          }
    > >          return(msg)
    > >      }
    > >      if (is.language(target))
    > >          return(all.equal.language(target, current, ...))
    > >
    > > would fix it.
    > >
    > > Duncan Murdoch
    > >
    > > ______________________________________________
    > > R-devel using r-project.org mailing list
    > > https://stat.ethz.ch/mailman/listinfo/r-devel