Precedence is a property of the parser and has nothing to do with the semantics assigned to various symbols. Using just core R functions you can see the precedence of '?' is between those of '=' and '<-'.
> # '=' has lower precedence than '?' > str(as.list(parse(text="a ? b = c")[[1]])) List of 3 $ : symbol = $ : language `?`(a, b) $ : symbol c > str(as.list(parse(text="a = b ? c")[[1]])) List of 3 $ : symbol = $ : symbol a $ : language `?`(b, c) > # '<-' has higher precedence than '?' > str(as.list(parse(text="a ? b <- c")[[1]])) List of 3 $ : symbol ? $ : symbol a $ : language b <- c > str(as.list(parse(text="a <- b ? c")[[1]])) List of 3 $ : symbol ? $ : language a <- b $ : symbol c Bill Dunlap TIBCO Software wdunlap tibco.com On Fri, Aug 30, 2019 at 4:41 AM Stephen Ellison <s.elli...@lgcgroup.com> wrote: > > From: R-devel [mailto:r-devel-boun...@r-project.org] On Behalf Of Ant F > > Sent: 29 August 2019 12:06 > > To: r-devel@r-project.org > > Subject: [Rd] ?Syntax wrong about `?`'s precedence ? > > ... > > See the following example : > > > > `?` <- `+` > > I'm curious; What did you expect to happen if you replace the function '?' > with the operator '+' ? > ? is surely now being evaluated as a user-defined function and not as an > operator. > Would you expect the results of doing that to be the same as evaluation > without replacement? > > S Ellison > > > > > ******************************************************************* > This email and any attachments are confidential. Any u...{{dropped:10}} ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
