I agree that the precedence looks reasonable. E.g.,
> str.language(quote(A > 0 & A<=B & B <= C => A <= C & 0 < C))
language: `=>`(A > 0 & A <= B & B <= C, A <= C ...
symbol: =>
language: A > 0 & A <= B & B <= C
symbol: &
language: A > 0 & A <= B
symbol: &
language: A > 0
symbol: >
symbol: A
double: 0
language: A <= B
symbol: <=
symbol: A
symbol: B
language: B <= C
symbol: <=
symbol: B
symbol: C
language: A <= C & 0 < C
symbol: &
language: A <= C
symbol: <=
symbol: A
symbol: C
language: 0 < C
symbol: <
double: 0
symbol: C
> str.language(quote(data |> tmp1 => f1(x, arg1=tmp1) |> f2(y) |> tmp3 =>
f3(z, arg3=tmp3)))
language: f3(z, arg3 = f2(f1(x, arg1 = data), y))
symbol: f3
symbol: z
language: arg3 = f2(f1(x, arg1 = data), y)
symbol: f2
language: f1(x, arg1 = data)
symbol: f1
symbol: x
symbol: arg1 = data
symbol: y
Where str.language is
str.language <- function(expr, name = "", indent = 0)
{
trim... <- function(string, width.cutoff) {
if (nchar(string) > width.cutoff) {
string <- sprintf("%.*s ...", width.cutoff-4, string)
}
string
}
cat(sep="", rep(" ", indent), typeof(expr), ": ",
if(length(name)==1 && nzchar(name)) { paste0(name, " = ") },
trim...(deparse1(expr, width.cutoff=40), width.cutoff=40),
"\n")
if (is.recursive(expr)) {
if (!is.list(expr)) {
expr <- as.list(expr)
}
nms <- names(expr)
for (i in seq_along(expr)) {
str.language(expr[[i]], name=nms[[i]], indent = indent + 1)
}
}
invisible(expr)
}
On Tue, Jan 12, 2021 at 1:16 PM Duncan Murdoch <murdoch.dun...@gmail.com>
wrote:
> On 12/01/2021 3:52 p.m., Bill Dunlap wrote:
> > '=>' can be defined as a function. E.g., it could be the logical
> "implies"
> > function:
> > > `=>` <- function(x, y) !x | y
> > > TRUE => FALSE
> > [1] FALSE
> > > FALSE => TRUE
> > [1] TRUE
> > It might be nice then to have deparse() display it as an infix operator
> > instead of the current prefix:
> > > deparse(quote(p => q))
> > [1] "`=>`(p, q)"
> > There was a user who recently wrote asking for an infix operator like ->
> or
> > => that would deparse nicely for use in some sort of model specification.
>
> The precedence of it as an operator is determined by what makes sense in
> the pipe construction. Currently precedence appears to be
>
>
> :: ::: access variables in a namespace
> $ @ component / slot extraction
> [ [[ indexing
> ^ exponentiation (right to left)
> - + unary minus and plus
> : sequence operator
> %any% special operators (including %% and %/%)
> * / multiply, divide
> + - (binary) add, subtract
> < > <= >= == != ordering and comparison
> ! negation
> & && and
> | || or
> => PIPE BIND
> |> PIPE
> ~ as in formulae
> -> ->> rightwards assignment
> <- <<- assignment (right to left)
> = assignment (right to left)
> ? help (unary and binary)
>
> (Most of this is taken from ?Syntax, but I added the new operators in
> based on the gram.y file). So
>
> A & B => C & D
>
> would appear to be parsed as
>
> (A & B) => (C & D)
>
> I think this also makes sense; do you?
>
> Duncan Murdoch
>
>
> >
> > When used with |>, the parser will turn the |> and => into an ordinary
> > looking function call so deparsing is irrelevant.
> > > deparse(quote(x |> tmp => f(7,arg2=tmp)))
> > [1] "f(7, arg2 = x)"
> >
> > -Bill
> >
> > On Tue, Jan 12, 2021 at 12:01 PM Dirk Eddelbuettel <e...@debian.org>
> wrote:
> >
> >>
> >> On 12 January 2021 at 20:38, Iñaki Ucar wrote:
> >> | On Tue, 12 Jan 2021 at 20:23, <luke-tier...@uiowa.edu> wrote:
> >> | >
> >> | > After some discussions we've settled on a syntax of the form
> >> | >
> >> | > mtcars |> subset(cyl == 4) |> d => lm(mpg ~ disp, data = d)
> >> | >
> >> | > to handle cases where the pipe lhs needs to be passed to an argument
> >> | > other than the first of the function called on the rhs. This seems a
> >> | > to be a reasonable balance between making these non-standard cases
> >> | > easy to see but still easy to write. This is now committed to
> R-devel.
> >> |
> >> | Interesting. Is the use of "d =>" restricted to pipelines? In other
> >> | words, I think that it shouldn't be equivalent to "function(d)", i.e.,
> >> | that this:
> >> |
> >> | x <- d => lm(mpg ~ disp, data = d)
> >> |
> >> | shouldn't work.
> >>
> >> Looks like your wish was already granted:
> >>
> >> > mtcars |> subset(cyl == 4) |> d => lm(mpg ~ disp, data = d)
> >>
> >> Call:
> >> lm(formula = mpg ~ disp, data = subset(mtcars, cyl == 4))
> >>
> >> Coefficients:
> >> (Intercept) disp
> >> 40.872 -0.135
> >>
> >> > d => lm(mpg ~ disp, data = d)
> >> Error in `=>`(d, lm(mpg ~ disp, data = d)) : could not find function
> "=>"
> >> > x <- d => lm(mpg ~ disp, data = d)
> >> Error in `=>`(d, lm(mpg ~ disp, data = d)) : could not find function
> "=>"
> >> >
> >>
> >> Dirk
> >>
> >> --
> >> https://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
> >>
> >> ______________________________________________
> >> R-devel@r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >>
> >
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> >
> > ______________________________________________
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> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
>
>
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