R devel - Apr 2023 - Generalised piping into operators

I'm afraid I don't understand. I know that parsing `+`(1, 1) returns a
result equivalent to `1 + 1`, but why does that impose a restriction on
parsing the pipe operator? What is the downside of allowing arbitrary RHS
functions?

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On 21/04/2023 12:16 p.m., Michael Milton wrote:
> I'm afraid I don't understand. I know that parsing `+`(1, 1)
returns a
> result equivalent to `1?+ 1`, but why does that impose a restriction on 
> parsing the pipe operator? What is the downside of allowing arbitrary 
> RHS functions?
I thought the decision to exclude "_ + 1" happens after enough parsing
has happened so that the code making the decision can't tell the 
difference between "_ + 1" and "`+`(_, 1)".  I might be
wrong about
that, but this suggests it:

   > quote(_ + 1)
   Error in quote("_" + 1) : invalid use of pipe placeholder
(<input>:1:0)
   > quote(`+`(_,  1))
   Error in quote("_" + 1) : invalid use of pipe placeholder
(<input>:1:0)

On the other hand, this works:

   > quote(x |> `+`(e1 = _, 1))
   x + 1

So maybe `+`() is fine after all.

Duncan Murdoch