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 <gmbec...@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 > <maech...@stat.math.ethz.ch> wrote: >> >> >>>>> Jim Hester <james.f.hes...@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 >> <gmbec...@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.hes...@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@r-project.org mailing list >> >>> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> >> >> >> >> >> >> >> >> -- >> >> Gabriel Becker, PhD >> >> Associate Scientist (Bioinformatics) >> >> Genentech Research >> >> > ______________________________________________ >> > R-devel@r-project.org mailing list >> > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > > -- > Gabriel Becker, PhD > Associate Scientist (Bioinformatics) > Genentech Research ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
