gaborcsardi, 8 months ago

@klmr

Yeah, you can have a string literal on the LHS, to assign values to non-syntactic names, I think that's from before we had backticks.

How the symbol name changes to NA is more surprising to me, maybe this is a bug:
❯ as.symbol(NA_character_)
NA

I think R should just not allow an NA string literal on the LHS of an assignment. It should probably be an error.

klmr, 8 months ago

@gaborcsardi I think R should not allow string literals in place of names, full stop. This change is even worth breaking a few packages on CRAN, IMHO, because the current behaviour is plain bananas and causes plenty of confusion.

gaborcsardi, 8 months ago

@klmr I have some vague memories that base R replaced the string literal symbols with backticks a long time ago,.

IDK if CRAN ever looked at the amount of breakage it would cause to make this an error.

klmr, 8 months ago

@gaborcsardi Yes, backticks came later. And there’s still some ancient core R code which uses "-quoted names, but that could obviously be fixed when deprecating/removing the syntax. But I don’t think there’s appetite for it.

klmr, 8 months ago

… but:

» NA_character_
[1] NA
» NA_character_
Error: object 'NA_character_' not found

Elendol, 8 months ago

@klmr is it because NA_character_ only the representation of NA for print and not the actual value?

klmr, 8 months ago

@Elendol Yes, and because R allows character literals instead of syntactic names in some places, including as the LHS of assignments. 🤮

Elendol, 8 months ago

@klmr oh no 😢

hrbrmstr, 8 months ago

@Elendol @klmr technically, NA_character_ is a reserved word https://stat.ethz.ch/R-manual/R-devel/library/base/html/Reserved.html

Reserved words are oddly allowed as non-syntactic names.

NA_character_ kind of only exists b/c comparisons (and NA values) in R vectors need to be typed; albeit in this kind of hacky way.

klmr, 8 months ago

@hrbrmstr But it only works with NA_character_, not NA, NA_real_, TRUE or any other reserved names. — And the reason is that NA_character_ (unlike all the others) is a character literal.

» NA = 1
Error in NA = 1 : invalid (do_set) left-hand side to assignment