Modified question mark operator

Description

⁠?⁠ was modified to allow definition of new operators (unary, binary or n-ary). We refer to those as "dubious" operators, both as a reference to the package name and to emphasize the fact that they're not parsed as proper operators. . Standard usage as documented in ?utils::Question still works.

Usage

`?`(e1, e2)

Arguments

dubious operators

Every accessible function, custom defined or base/packaged, can be called as an infix operator, for example 1:5 %%intersect? 3:7 is equivalent to intersect(1:5, 3:7). In that case, ⁠%%intersect?⁠ will have the precedence of %%, which is the most intuitive, but any precedence including and below unary + can be used, for instance ⁠*intersect?⁠ will have the precedence of *.

Unary operators can be used to, for instance ~head? x is the same as head(x). This form can also be used with several arguments, but in this case we need to write ⁠~head? {x ; n)⁠ for instance, which is convenient to go to the next line without the need of a comma.

dubious pipes

We can pipe with a chosen precedence by using a dubious pipe, for instance x + y ~saveRDS? file will save x + y, not just x

We can pipe with a chosen precedence by using a dubious pipe, for instance x + y ~saveRDS? file will save x + y, not just x

dubious syntaxes

defining "?add: ({x})({y})" <- "{x} + {y}" will allow us to call ?add: (a)(b) to add a and b.

Examples

cars +head? 2
+head? cars
+head? {
  cars
  2}

Register Dubious Syntaxes

Description

To use a dubious syntax in a package, use this function in the definition of .onAttach

Usage

register_dubious_syntaxes(syntaxes)

Arguments

Examples

## Not run: 
# define your syntax as you would define a normal function
`?add> {x} : {y}` <- function(x, y) x + y

# register the syntax in your .onAttach definition
.onAttach <- function(libname, pkgname) {
doubt::register_dubious_syntaxes("?add> {x} : {y}")
invisible()
}

## End(Not run)