match()/%in% with language objects?

Did you support Ben's  wish to allow 'symbol' (aka 'name') objects as well,
or even more general language objects (as by the subject's wording) ?
Do you mean should match treat
    match(quote(foo), list(as.name("bar"), as.name("foo"))) # error
the same as
    match(list(quote(foo)), list(as.name("bar"), as.name("foo"))) # 2
?  I don't think that would be good - 'x' needs to be a list or expression
in the length!=1 cases, so it should be one in all cases.

On the other hand it would be nice to fix up things like
  > list(list(quote(foo)), quote(list(foo))) %in% list(quote(list(foo)))
  [1] TRUE TRUE
either by using calls to identical() in the match/hashing code or
adding "quoteExpressions" when deparsing the language objects.
  x <- list(list(quote(foo)), quote(list(foo)))
  table <- list(quote(list(foo)))
  x %in% table
  #[1] TRUE TRUE
  lapply(x, deparse) %in% lapply(table, deparse)
  #[1] TRUE TRUE
  lapply(x, deparse, control="quoteExpressions") %in% lapply(table,
deparse, control="quoteExpressions")
  #[1] FALSE  TRUE

duplicated() already seems to do the right thing in that case:
  duplicated(x)
  #[1] FALSE FALSE
  duplicated(x[c(1,2,1)])
  #[1] FALSE FALSE  TRUE

Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Wed, Aug 26, 2015 at 1:54 AM, Martin Maechler <maechler at stat.math.ethz.ch
wrote:
William Dunlap <wdunlap at tibco.com>
    on Tue, 25 Aug 2015 09:47:23 -0700 writes:

    > match(x,table) and x%in%table work when x and table are lists of
language
    > objects or expressions.  E.g.,

    > expression(quote(1+2), quote(log2(16))) %in% expression(3,
quote(1+2), c(4L,5L,6L,7L))
    > #[1]  TRUE FALSE
    > list(quote(1+2), quote(log2(16))) %in% list(3, quote(1+2),
c(4L,5L,6L,7L))
    > #[1]  TRUE FALSE
    > match(list(quote(1+2), quote(log2(16))),  list(3, quote(1+2),
c(4L,5L,6L,7L)))
    > #[1]  2 NA
yes, or slightly more naturally for the first case,

 > expression(1+2, log2(16)) %in% expression(3, 1+2, c(4L,5L,6L,7L))
 [1]  TRUE FALSE

    > With your example data:
    > spList[1] %in% spList
    > #[1] TRUE
    > list(quote(foo)) %in% spList
    > #[1] TRUE
    > list(quote(nosuchsymbol)) %in% spList
    > #[1] FALSE
yes  indeed, that works because list()s and expression()s are
"vector"s in the wide sense, as "we all" know.

Did you support Ben's  wish to allow 'symbol' (aka 'name') objects as well,
or even more general language objects (as by the subject's wording) ?

Internally, in these cases the matches do happen with character
coerced objects eventually; still I'd tend to agree that allowing some of
these as arguments to match() in addition to the
wide-sense-vectors (and NULL !) would make sense.

Martin

    > Bill Dunlap
    > TIBCO Software
    > wdunlap tibco.com

    > On Tue, Aug 25, 2015 at 9:12 AM, Ben Bolker <bbolker at gmail.com>
wrote:

    >> -----BEGIN PGP SIGNED MESSAGE-----
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    >>
    >>
    >> I haven't yet dug into the internals of match() yet to see what's
    >> going on, but I'm wondering whether there's a design reason why I
    >> can't use %in% (which is a wrapper for match()) on language objects.
    >>
    >> I'd like to test whether a language object is in a list of language
    >> objects, but I get the error "'match' requires vector arguments":
    >>
    >> specials <- c("foo","bar")
    >> spList <- lapply(specials,as.name)  ## convert to language objects
    >> "a" %in% spList  ## works (FALSE)
    >> spList[[1]] %in% spList ##   'match' requires vector arguments
    >> quote(foo) %in% spList  ## ditto
    >> quote(foo) == spList[[1]]  ## TRUE
    >>
    >> obviously I can go the other way, converting my target into text:
    >>
    >> deparse(spList[[1]]) %in% specials  ## TRUE
    >>
    >> I could also write my own function to loop through the list and stop
    >> when I find it.  But I'd prefer to use built-in functionality if
possible.
    >>
    >> Does anyone have any clues/see what I'm missing?
    >>
    >> cheers
    >> Ben Bolker
    >> -----BEGIN PGP SIGNATURE-----
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    >> iQEcBAEBAgAGBQJV3JQLAAoJEOCV5YRblxUHTEkIAJluX0F2bLGW1jt1FP2UEZs1
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    >> =w3OR
    >> -----END PGP SIGNATURE-----
    >>
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match()/%in% with language objects?

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