[Rd] Support for user defined unary functions
Michael Lawrence
lawrence.michael at gene.com
Thu Mar 16 23:18:00 CET 2017
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
>
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