From gmbecker at ucdavis.edu  Fri Mar 17 21:09:25 2017
From: gmbecker at ucdavis.edu (Gabriel Becker)
Date: Fri, 17 Mar 2017 13:09:25 -0700
Subject: [Rd] Support for user defined unary functions
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Message-ID: <CADwqtCNgakpGMTZMsebq7KeSybJcs1QXk9jvrPCoLWjaQwvVWQ@mail.gmail.com>

Bill,

Right. My example was the functional form for clarity.

There is a desire for a unary-operator form. (rlang's !! and !!! operators
described in the comments in the file I linked to).  I can't really make
that argument because I'm not one of the people who wanted that. You'd have
to talk to the authors of the rlang package to find out their reasons for
thinking that is important. All I know is that empirically, they seem to
feel that way. There may also be issues with the use of . specifically,
because this is in the "tidyverse" context where piping is common and . is
used for something else there, but again that's conjecture on my part.

Best,
~G

On Fri, Mar 17, 2017 at 12:53 PM, William Dunlap <wdunlap at tibco.com> wrote:

> Your example
>    x = 5
>    exp = parse(text="f(uq(x)) + y +z") # expression: f(uq(x)) +y + z
>    do_unquote(expr)
>     # -> the language object f(5) + y + z
> could be done with the following wrapper for bquote
>    my_do_unquote <- function(language, envir = parent.frame()) {
>       if (is.expression(language)) {
>          # bquote does not go into expressions, only calls
>          as.expression(lapply(language, my_do_unquote))
>       } else {
>          do.call(bquote, list(language, where=envir))
>       }
>    }
> as in
>    > x <- 5
>    > exp <- parse(text="f(.(x)) + y +z") # dot is uq for bquote
>    > exp
>    expression(f(.(x)) + y +z)
>    > my_do_unquote(exp)
>    expression(f(5) + y + z)
> Or do uq() and do_unquote() do more than that?  E.g., would
> uq() carry information about environments?
>
> [I think expressions should map to expressions and calls to calls.
> Otherwise what would we do with multicall expressions?]
>
> We probably need to come up with a better name than 'non-standard
> evaluation' since there are lots of non-standard ways of doing things.
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
>
> On Fri, Mar 17, 2017 at 12:14 PM, Gabriel Becker <gmbecker at ucdavis.edu>
> wrote:
> > William,
> >
> > Unbeknownst to me when I sent this, Jonathon Carrol started a specific
> > thread about unquoting and a proposal for supporting it at the language
> > level, which I think is a better place to discuss unquoting specifically.
> > That said, the basics as I understand them in the context of non-standard
> > evaluation, unquoting (or perhaps interpolation) is essentially
> substituting
> > part of an unevaluated expression with its evaluated value inlined. The
> > unquote operator, then, is the way of marking which parts of the
> expression
> > should be substituted in that way (i.e. interpolated).
> >
> > i.e. if uq() is the unquote "operator" and do_unquote interpolates, then
> if
> > we have
> >
> > x = 5
> >
> > exp = parse(text="f(uq(x)) + y +z") # expression: f(uq(x)) +y + z
> >
> >
> > Then do_unquote would give you the expression f(5) + y + z
> >
> > In terms of what it does that the tilde does not, it would give you the
> > ability to partially evaluate the captured formula/expression, without
> fully
> > doing so.  See the roxygen comments in Hadley and Lionel's rlang package
> > here: https://github.com/hadley/rlang/blob/master/R/tidy-unquote.R
> >
> > The desired precedence of such a unary operator is not clear to me. The
> way
> > rlang implements the !! now, it is quite low, so in the examples you see
> > there the ~list(!! x + x) is transformed to ~list(10), not ~list(5+x) as
> I
> > would have expected.  I'm confused by this given what I understand the
> > purpose to be, but that probably just means I'm not the right person to
> ask.
> >
> > Hope that helps.
> >
> > Best,
> > ~G
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > On Fri, Mar 17, 2017 at 8:55 AM, William Dunlap <wdunlap at tibco.com>
> wrote:
> >>
> >> >After off list discussions with Jonathan Carrol and with
> >> >Michael Lawrence I think it's doable, unambiguous,
> >> >and even imo pretty intuitive for an "unquote" operator.
> >>
> >> For those of us who are not CS/Lisp mavens, what is an
> >> "unquote" operator?  Can you expression quoting and unquoting
> >> in R syntax and show a few examples where is is useful,
> >> intuitive, and fits in to R's functional design?  In particular,
> >> what does it give us that the current tilde function does not?
> >>
> >>
> >> Bill Dunlap
> >> TIBCO Software
> >> wdunlap tibco.com
> >>
> >>
> >> On Fri, Mar 17, 2017 at 6:46 AM, Gabriel Becker <gmbecker at ucdavis.edu>
> >> wrote:
> >> > Jim,
> >> >
> >> > One more note about precedence. It prevents a solution like the one
> you
> >> > proposed from solving all of the problems you cited. By my reckoning,
> a
> >> > "What comes next is for NSE" unary operator needs an extremely low
> >> > precedence, because it needs to greedily grab "everything" (or a large
> >> > amount) that comes after it. Normal-style unary operators, on the
> other
> >> > hand, explicitly don't want that.
> >> >
> >> > From what I can see, your patch provides support for the latter but
> not
> >> > the
> >> > former.
> >> >
> >> > That said I think there are two issues here. One is can users define
> >> > unary
> >> > operators. FWIW my opinion on that is roughly neutral to slightly
> >> > positive.
> >> > The other issue is can we have quasi quotation of the type that Hadley
> >> > and
> >> > Lionel need in the language. This could be solved without allowing
> >> > user-defined unary specials, and we would probably want it to be, as I
> >> > doubt
> >> > ~ %!%x + %!%y + z is  particularly aesthetically appealing to most (it
> >> > isn't
> >> > to me). I'd propose coopting unary @ for that myself. After off list
> >> > discussions with Jonathan Carrol and with Michael Lawrence I think
> it's
> >> > doable, unambiguous, and even imo pretty intuitive for an "unquote"
> >> > operator.
> >> >
> >> > Best,
> >> > ~G
> >> >
> >> > On Fri, Mar 17, 2017 at 5:10 AM, Jim Hester <james.f.hester at gmail.com
> >
> >> > wrote:
> >> >>
> >> >> I agree there is no reason they _need_ to be the same precedence, but
> >> >> I think SPECIALS are already have the proper precedence for both
> unary
> >> >> and binary calls. Namely higher than all the binary operators (except
> >> >> for `:`), but lower than the other unary operators. Even if we gave
> >> >> unary specials their own precedence I think it would end up in the
> >> >> same place.
> >> >>
> >> >>     `%l%` <- function(x) tail(x, n = 1)
> >> >>     %l% 1:5
> >> >>     #> [1] 5
> >> >>     %l% -5:-10
> >> >>     #> [1] -10
> >> >>
> >> >> On Thu, Mar 16, 2017 at 6:57 PM, William Dunlap <wdunlap at tibco.com>
> >> >> wrote:
> >> >> > I am biased against introducing new syntax, but if one is
> >> >> > experimenting with it one should make sure the precedence feels
> >> >> > right.
> >> >> > I think the unary and binary minus-sign operators have different
> >> >> > precedences so I see no a priori reason to make the unary and
> binary
> >> >> > %xxx% operators to be the same.
> >> >> > Bill Dunlap
> >> >> > TIBCO Software
> >> >> > wdunlap tibco.com
> >> >> >
> >> >> >
> >> >> > On Thu, Mar 16, 2017 at 3:18 PM, Michael Lawrence
> >> >> > <lawrence.michael at gene.com> wrote:
> >> >> >> I guess this would establish a separate "namespace" of symbolic
> >> >> >> prefix
> >> >> >> operators, %*% being an example in the infix case. So you could
> have
> >> >> >> stuff
> >> >> >> like %?%, but for non-symbolic (spelled out stuff like %foo%),
> it's
> >> >> >> hard to
> >> >> >> see the advantage vs. foo(x).
> >> >> >>
> >> >> >> Those examples you mention should probably be addressed
> (eventually)
> >> >> >> in
> >> >> >> the
> >> >> >> core language, and it looks like people are already able to
> >> >> >> experiment,
> >> >> >> so
> >> >> >> I'm not sure there's a significant impetus for this change.
> >> >> >>
> >> >> >> Michael
> >> >> >>
> >> >> >>
> >> >> >> On Thu, Mar 16, 2017 at 10:51 AM, Jim Hester
> >> >> >> <james.f.hester at gmail.com>
> >> >> >> wrote:
> >> >> >>
> >> >> >>> I used the `function(x)` form to explicitly show the function was
> >> >> >>> being called with only one argument, clearly performance
> >> >> >>> implications
> >> >> >>> are not relevant for these examples.
> >> >> >>>
> >> >> >>> I think of this mainly as a gap in the tooling we provide users
> and
> >> >> >>> package authors. R has native prefix `+1`, functional `f(1)` and
> >> >> >>> infix
> >> >> >>> `1 + 1` operators, but we only provide a mechanism to create user
> >> >> >>> defined functional and infix operators.
> >> >> >>>
> >> >> >>> One could also argue that the user defined infix operators are
> also
> >> >> >>> ugly and could be replaced by `f(a, b)` calls as well; beauty is
> in
> >> >> >>> the eye of the beholder.
> >> >> >>>
> >> >> >>> The unquote example [1] shows one example where this gap in
> tooling
> >> >> >>> caused authors to co-opt existing unary exclamation operator,
> this
> >> >> >>> same gap is part of the reason the formula [2] and question mark
> >> >> >>> [3]
> >> >> >>> operators have been used elsewhere in non standard contexts.
> >> >> >>>
> >> >> >>> If the language provided package authors with a native way to
> >> >> >>> create
> >> >> >>> unary operators like it already does for the other operator types
> >> >> >>> these machinations would be unnecessary.
> >> >> >>>
> >> >> >>> [1]:
> >> >> >>> https://github.com/hadley/rlang/blob/master/R/tidy-unquote.R#L17
> >> >> >>> [2]: https://cran.r-project.org/package=ensurer
> >> >> >>> [3]: https://cran.r-project.org/package=types
> >> >> >>>
> >> >> >>> On Thu, Mar 16, 2017 at 1:04 PM, Gabriel Becker
> >> >> >>> <gmbecker at ucdavis.edu>
> >> >> >>> wrote:
> >> >> >>> > Martin,
> >> >> >>> >
> >> >> >>> > Jim can speak directly to his motivations; I don't claim to be
> >> >> >>> > able
> >> >> >>> > to do
> >> >> >>> > so. That said, I suspect this is related to a conversation on
> >> >> >>> > twitter
> >> >> >>> about
> >> >> >>> > wanting an infix "unquote" operator in the context of the
> >> >> >>> > non-standard
> >> >> >>> > evaluation framework Hadley Wickham and Lionel Henry (and
> >> >> >>> > possibly
> >> >> >>> others)
> >> >> >>> > are working on.
> >> >> >>> >
> >> >> >>> > They're currently using !!! and !! for things related to this,
> >> >> >>> > but
> >> >> >>> > this
> >> >> >>> > effectively requires non-standard parsing, as ~!!x is
> interpreted
> >> >> >>> > as
> >> >> >>> > ~(`!!`(x)) rather than ~(!(!(x)) as the R parser understands
> it.
> >> >> >>> > Others
> >> >> >>> and
> >> >> >>> > I pointed out this was less than desirable, but if something
> like
> >> >> >>> > it
> >> >> >>> > was
> >> >> >>> > going to happen it would hopefully happen in the language
> >> >> >>> > specification,
> >> >> >>> > rather than in a package (and also hopefully not using !!
> >> >> >>> > specifically).
> >> >> >>> >
> >> >> >>> > Like you, I actually tend to prefer the functional form myself
> in
> >> >> >>> > most
> >> >> >>> > cases. There are functional forms that would work for the above
> >> >> >>> > case
> >> >> >>> (e.g.,
> >> >> >>> > something like the .() that DBI uses), but that's probably off
> >> >> >>> > topic
> >> >> >>> here,
> >> >> >>> > and not a decision I'm directly related to anyway.
> >> >> >>> >
> >> >> >>> > Best,
> >> >> >>> > ~G
> >> >> >>> >
> >> >> >>> >
> >> >> >>> >
> >> >> >>> > On Thu, Mar 16, 2017 at 9:51 AM, Martin Maechler
> >> >> >>> > <maechler at stat.math.ethz.ch> wrote:
> >> >> >>> >>
> >> >> >>> >> >>>>> Jim Hester <james.f.hester at gmail.com>
> >> >> >>> >> >>>>>     on Thu, 16 Mar 2017 12:31:56 -0400 writes:
> >> >> >>> >>
> >> >> >>> >>     > Gabe,
> >> >> >>> >>     > The unary functions have the same precedence as normal
> >> >> >>> >> SPECIALS
> >> >> >>> >>     > (although the new unary forms take precedence over
> binary
> >> >> >>> SPECIALS).
> >> >> >>> >>     > So they are lower precedence than unary + and -. Yes,
> both
> >> >> >>> >> of
> >> >> >>> >> your
> >> >> >>> >>     > examples are valid with this patch, here are the results
> >> >> >>> >> and
> >> >> >>> quoted
> >> >> >>> >>     > forms to see the precedence.
> >> >> >>> >>
> >> >> >>> >>     > `%chr%` <- function(x) as.character(x)
> >> >> >>> >>
> >> >> >>> >>   [more efficient would be     `%chr%` <- as.character]
> >> >> >>> >>
> >> >> >>> >>     > `%identical%` <- function(x, y) identical(x, y)
> >> >> >>> >>     > quote("100" %identical% %chr% 100)
> >> >> >>> >>     > #>  "100" %identical% (`%chr%`(100))
> >> >> >>> >>
> >> >> >>> >>     > "100" %identical% %chr% 100
> >> >> >>> >>     > #> [1] TRUE
> >> >> >>> >>
> >> >> >>> >>     > `%num%` <- as.numeric
> >> >> >>> >>     > quote(1 + - %num% "5")
> >> >> >>> >>     > #> 1 + -(`%num%`("5"))
> >> >> >>> >>
> >> >> >>> >>     > 1 + - %num% "5"
> >> >> >>> >>     > #> [1] -4
> >> >> >>> >>
> >> >> >>> >>     > Jim
> >> >> >>> >>
> >> >> >>> >> I'm sorry to be a bit of a spoiler to "coolness", but
> >> >> >>> >> you may know that I like to  applaud Norm Matloff for his book
> >> >> >>> >> title "The Art of R Programming",
> >> >> >>> >> because for me good code should also be beautiful to some
> >> >> >>> >> extent.
> >> >> >>> >>
> >> >> >>> >> I really very much prefer
> >> >> >>> >>
> >> >> >>> >>        f(x)
> >> >> >>> >> to    %f% x
> >> >> >>> >>
> >> >> >>> >> and hence I really really really cannot see why anybody would
> >> >> >>> >> prefer
> >> >> >>> >> the ugliness of
> >> >> >>> >>
> >> >> >>> >>            1 + - %num% "5"
> >> >> >>> >> to
> >> >> >>> >>            1 + -num("5")
> >> >> >>> >>
> >> >> >>> >> (after setting  num <- as.numeric )
> >> >> >>> >>
> >> >> >>> >> Martin
> >> >> >>> >>
> >> >> >>> >>
> >> >> >>> >>     > On Thu, Mar 16, 2017 at 12:01 PM, Gabriel Becker
> >> >> >>> >> <gmbecker at ucdavis.edu> wrote:
> >> >> >>> >>     >> Jim,
> >> >> >>> >>     >>
> >> >> >>> >>     >> This seems cool. Thanks for proposing it. To be
> concrete,
> >> >> >>> >> he
> >> >> >>> >> user-defined
> >> >> >>> >>     >> unary operations would be of the same precedence (or
> just
> >> >> >>> slightly
> >> >> >>> >> below?)
> >> >> >>> >>     >> built-in unary ones? So
> >> >> >>> >>     >>
> >> >> >>> >>     >> "100" %identical% %chr% 100
> >> >> >>> >>     >>
> >> >> >>> >>     >> would work and return TRUE under your patch?
> >> >> >>> >>     >>
> >> >> >>> >>     >> And  with %num% <- as.numeric, then
> >> >> >>> >>     >>
> >> >> >>> >>     >> 1 + - %num% "5"
> >> >> >>> >>     >>
> >> >> >>> >>     >> would also be legal (though quite ugly imo) and work?
> >> >> >>> >>     >>
> >> >> >>> >>     >> Best,
> >> >> >>> >>     >> ~G
> >> >> >>> >>     >>
> >> >> >>> >>     >> On Thu, Mar 16, 2017 at 7:24 AM, Jim Hester
> >> >> >>> >> <james.f.hester at gmail.com>
> >> >> >>> >>     >> wrote:
> >> >> >>> >>     >>>
> >> >> >>> >>     >>> R has long supported user defined binary (infix)
> >> >> >>> >> functions,
> >> >> >>> >> defined
> >> >> >>> >>     >>> with `%fun%`. A one line change [1] to R's grammar
> >> >> >>> >> allows
> >> >> >>> >> users
> >> >> >>> to
> >> >> >>> >>     >>> define unary (prefix) functions in the same manner.
> >> >> >>> >>     >>>
> >> >> >>> >>     >>> `%chr%` <- function(x) as.character(x)
> >> >> >>> >>     >>> `%identical%` <- function(x, y) identical(x, y)
> >> >> >>> >>     >>>
> >> >> >>> >>     >>> %chr% 100
> >> >> >>> >>     >>> #> [1] "100"
> >> >> >>> >>     >>>
> >> >> >>> >>     >>> %chr% 100 %identical% "100"
> >> >> >>> >>     >>> #> [1] TRUE
> >> >> >>> >>     >>>
> >> >> >>> >>     >>> This seems a natural extension of the existing
> >> >> >>> >> functionality and
> >> >> >>> >>     >>> requires only a minor change to the grammar. If this
> >> >> >>> >> change
> >> >> >>> seems
> >> >> >>> >>     >>> acceptable I am happy to provide a complete patch with
> >> >> >>> >> suitable
> >> >> >>> >> tests
> >> >> >>> >>     >>> and documentation.
> >> >> >>> >>     >>>
> >> >> >>> >>     >>> [1]:
> >> >> >>> >>     >>> Index: src/main/gram.y
> >> >> >>> >>     >>>
> >> >> >>> >>
> >> >> >>> >> ============================================================
> =======
> >> >> >>> >>     >>> --- src/main/gram.y     (revision 72358)
> >> >> >>> >>     >>> +++ src/main/gram.y     (working copy)
> >> >> >>> >>     >>> @@ -357,6 +357,7 @@
> >> >> >>> >>     >>> |       '+' expr %prec UMINUS           { $$ =
> >> >> >>> >> xxunary($1,$2);
> >> >> >>> >>     >>> setId( $$, @$); }
> >> >> >>> >>     >>> |       '!' expr %prec UNOT             { $$ =
> >> >> >>> >> xxunary($1,$2);
> >> >> >>> >>     >>> setId( $$, @$); }
> >> >> >>> >>     >>> |       '~' expr %prec TILDE            { $$ =
> >> >> >>> >> xxunary($1,$2);
> >> >> >>> >>     >>> setId( $$, @$); }
> >> >> >>> >>     >>> +       |       SPECIAL expr                    { $$ =
> >> >> >>> >> xxunary($1,$2);
> >> >> >>> >>     >>> setId( $$, @$); }
> >> >> >>> >>     >>> |       '?' expr                        { $$ =
> >> >> >>> >> xxunary($1,$2);
> >> >> >>> >>     >>> setId( $$, @$); }
> >> >> >>> >>     >>>
> >> >> >>> >>     >>> |       expr ':'  expr                  { $$ =
> >> >> >>> >>     >>> xxbinary($2,$1,$3);      setId( $$, @$); }
> >> >> >>> >>     >>>
> >> >> >>> >>     >>> ______________________________________________
> >> >> >>> >>     >>> R-devel at r-project.org mailing list
> >> >> >>> >>     >>> https://stat.ethz.ch/mailman/listinfo/r-devel
> >> >> >>> >>     >>
> >> >> >>> >>     >>
> >> >> >>> >>     >>
> >> >> >>> >>     >>
> >> >> >>> >>     >> --
> >> >> >>> >>     >> Gabriel Becker, PhD
> >> >> >>> >>     >> Associate Scientist (Bioinformatics)
> >> >> >>> >>     >> Genentech Research
> >> >> >>> >>
> >> >> >>> >>     > ______________________________________________
> >> >> >>> >>     > R-devel at r-project.org mailing list
> >> >> >>> >>     > https://stat.ethz.ch/mailman/listinfo/r-devel
> >> >> >>> >
> >> >> >>> >
> >> >> >>> >
> >> >> >>> >
> >> >> >>> > --
> >> >> >>> > Gabriel Becker, PhD
> >> >> >>> > Associate Scientist (Bioinformatics)
> >> >> >>> > Genentech Research
> >> >> >>>
> >> >> >>> ______________________________________________
> >> >> >>> R-devel at r-project.org mailing list
> >> >> >>> https://stat.ethz.ch/mailman/listinfo/r-devel
> >> >> >>>
> >> >> >>
> >> >> >>         [[alternative HTML version deleted]]
> >> >> >>
> >> >> >> ______________________________________________
> >> >> >> R-devel at r-project.org mailing list
> >> >> >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >> >>
> >> >> ______________________________________________
> >> >> R-devel at r-project.org mailing list
> >> >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >> >
> >> >
> >> >
> >> >
> >> > --
> >> > Gabriel Becker, PhD
> >> > Associate Scientist (Bioinformatics)
> >> > Genentech Research
> >
> >
> >
> >
> > --
> > Gabriel Becker, PhD
> > Associate Scientist (Bioinformatics)
> > Genentech Research
>



-- 
Gabriel Becker, PhD
Associate Scientist (Bioinformatics)
Genentech Research

	[[alternative HTML version deleted]]



[Rd] Support for user defined unary functions
Gabriel Becker