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 <[email protected]> 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 <[email protected]> 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 <[email protected]> > wrote: > > That parser already flips -> to <- before creating the parse tree. > > > > Gabor > > > > On Mon, Apr 13, 2020 at 8:39 AM Adrian Dușa <[email protected]> > 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 > > > > > > ______________________________________________ > > > [email protected] mailing list > > > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > ______________________________________________ > > [email protected] 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 > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
