R has long supported user defined binary (infix) functions, defined
with `%fun%`. A one line change [1] to R's grammar allows users to
define unary (prefix) functions in the same manner.
`%chr%` <- function(x) as.character(x)
`%identical%` <- function(x, y) identical(x, y)
%chr% 100
Jim,
This seems cool. Thanks for proposing it. To be concrete, he user-defined
unary operations would be of the same precedence (or just slightly below?)
built-in unary ones? So
"100" %identical% %chr% 100
would work and return TRUE under your patch?
And with %num% <- as.numeric, then
1 + - %
Gabe,
The unary functions have the same precedence as normal SPECIALS
(although the new unary forms take precedence over binary SPECIALS).
So they are lower precedence than unary + and -. Yes, both of your
examples are valid with this patch, here are the results and quoted
forms to see the precede
> Jim Hester
> on Thu, 16 Mar 2017 12:31:56 -0400 writes:
> Gabe,
> The unary functions have the same precedence as normal SPECIALS
> (although the new unary forms take precedence over binary SPECIALS).
> So they are lower precedence than unary + and -. Yes, both of yo
Martin,
Jim can speak directly to his motivations; I don't claim to be able to do
so. That said, I suspect this is related to a conversation on twitter about
wanting an infix "unquote" operator in the context of the non-standard
evaluation framework Hadley Wickham and Lionel Henry (and possibly ot
I used the `function(x)` form to explicitly show the function was
being called with only one argument, clearly performance implications
are not relevant for these examples.
I think of this mainly as a gap in the tooling we provide users and
package authors. R has native prefix `+1`, functional `f(
I guess this would establish a separate "namespace" of symbolic prefix
operators, %*% being an example in the infix case. So you could have stuff
like %?%, but for non-symbolic (spelled out stuff like %foo%), it's hard to
see the advantage vs. foo(x).
Those examples you mention should probably be
I am biased against introducing new syntax, but if one is
experimenting with it one should make sure the precedence feels right.
I think the unary and binary minus-sign operators have different
precedences so I see no a priori reason to make the unary and binary
%xxx% operators to be the same.
Bill
I don't have a positive or negative opinion on this yet, but I do have a
question. If I define both unary and binary operators with the same
name (in different frames, presumably), what would happen?
Is "a %chr% b" a syntax error if unary %chr% is found first? If both
might be found, does "a
(please be gentle, it's my first time)
I am interested in discussions (possibly reiterating past threads --
searching didn't turn up much) on the possibility of supporting standard
evaluation unquoting at the language level. This has been brought up in a
recent similar thread here [1] and on Twitt
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