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
#> [1] "100"
%chr% 100 %identical% "100"
#> [1] TRUE
This seems a natural extension of the existing functionality and
requires only a minor change to the grammar. If this change seems
acceptable I am happy to provide a complete patch with suitable tests
and documentation.
[1]:
Index: src/main/gram.y
===================================================================
--- src/main/gram.y (revision 72358)
+++ src/main/gram.y (working copy)
@@ -357,6 +357,7 @@
| '+' expr %prec UMINUS { $$ = xxunary($1,$2);
setId( $$, @$); }
| '!' expr %prec UNOT { $$ = xxunary($1,$2);
setId( $$, @$); }
| '~' expr %prec TILDE { $$ = xxunary($1,$2);
setId( $$, @$); }
+ | SPECIAL expr { $$ = xxunary($1,$2);
setId( $$, @$); }
| '?' expr { $$ = xxunary($1,$2);
setId( $$, @$); }
| expr ':' expr { $$ =
xxbinary($2,$1,$3); setId( $$, @$); }