[Rd] detect ->

[William Dunlap]

Using => and <= instead of -> and <- would make things easier, although the
precedence would be different.

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Mon, Apr 13, 2020 at 1:43 AM Adrian Dușa <dusa.adrian using gmail.com> wrote:

> Thank you for your replies, this actually has little to do with the
> regular R code but more to signal what in my package QCA is referred to as
> a necessity relation A <- B (A is necessary for B) and sufficiency A -> B
> (A is sufficient for B).
>
> If switched by the parser, A -> B becomes B <- A which makes B necessary
> for A, while the intention is to signal sufficiency for B.
>
> Capturing in a quoted string is trivial, but I am now experimenting with
> substitute() to allow unquoted expressions.
>
> This is especially useful when selecting A and B from the columns of a
> data frame, using: c(A, B) instead of c("A", "B") with a lot more quotes
> for more complex expressions using more columns.
>
> I would be grateful for any pointer to a project that processes the code
> while it is still raw text. I could maybe learn from their code and adapt
> to my use case.
>
> Best wishes,
> Adrian
>
> > On 13 Apr 2020, at 11:23, Gabriel Becker <gabembecker using gmail.com> wrote:
> >
> > Adrian,
> >
> > Indeed, this has come up in a few places, but as Gabor says, there is no
> such thing as right hand assignment at any point after parsing is complete.
> >
> > This means the only feasible way to detect it, which a few projects do I
> believe, is process the code while it is still raw text, before it goes
> into the parser, and have clever enough regular expressions.
> >
> > The next question, then, is why are you trying to detect right
> assignment. Doing so can be arguably useful fo linting, its true.
> Otherwise, though, because its not really a "real thing" when the R code is
> being executed, its not something thats generally meaningful to detect in
> most cases.
> >
> > Best,
> > ~G
> >
> > On Mon, Apr 13, 2020 at 12:52 AM Gábor Csárdi <csardi.gabor using gmail.com>
> wrote:
> > That parser already flips -> to <- before creating the parse tree.
> >
> > Gabor
> >
> > On Mon, Apr 13, 2020 at 8:39 AM Adrian Dușa <dusa.adrian using gmail.com>
> wrote:
> > >
> > > I searched and tried for hours, to no avail although it looks simple.
> > >
> > > (function(x) substitute(x))(A <- B)
> > > #A <- B
> > >
> > > (function(x) substitute(x))(A -> B)
> > > # B <- A
> > >
> > > In the first example, A occurs on the LHS, but in the second example A
> is somehow evaluated as if it occured on the RHS, despite my understanding
> that substitute() returns the unevaluated parse tree.
> > >
> > > Is there any way, or is it even possible to detect the right hand
> assignment, to determine whether A occurs on the LHS?
> > >
> > > Thanks in advance for any hint,
> > > Adrian
> > >
> > > —
> > > Adrian Dusa
> > > University of Bucharest
> > > Romanian Social Data Archive
> > > Soseaua Panduri nr. 90-92
> > > 050663 Bucharest sector 5
> > > Romania
> > > https://adriandusa.eu
> > >
> > > ______________________________________________
> > > R-devel using r-project.org mailing list
> > > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
> > ______________________________________________
> > R-devel using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
>
> —
> Adrian Dusa
> University of Bucharest
> Romanian Social Data Archive
> Soseaua Panduri nr. 90-92
> 050663 Bucharest sector 5
> Romania
> https://adriandusa.eu
>
> ______________________________________________
> R-devel using r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

	[[alternative HTML version deleted]]