detect ->

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 at 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 G?bor Cs?rdi <csardi.gabor at gmail.com>

wrote:

That parser already flips -> to <- before creating the parse tree.

Gabor

On Mon, Apr 13, 2020 at 8:39 AM Adrian Du?a <dusa.adrian at 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

?
Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Soseaua Panduri nr. 90-92
050663 Bucharest sector 5
Romania
https://adriandusa.eu