#lang scribble/doc
@(require "common.rkt" scribble/eval (for-label syntax/transformer))

@(define the-eval (make-base-eval))
@(the-eval '(require syntax/transformer (for-syntax racket/base syntax/transformer)))

@title[#:tag "syntax/transformer"]{Creating Macro Transformers}

@defmodule[syntax/transformer]

@defproc[(make-variable-like-transformer [reference-stx syntax?]
                                         [setter-stx (or/c syntax? #f) #f])
         set!-transformer?]{

Creates a transformer that replaces references to the macro identifier
with @racket[reference-stx]. Uses of the macro in operator position
are interpreted as an application with @racket[reference-stx] as the
function and the arguments as given.

If the macro identifier is used as the target of a @racket[set!] form,
then the @racket[set!] form expands into the application of
@racket[setter-stx] to the @racket[set!] expression's right-hand side,
if @racket[setter-stx] is syntax; otherwise, the identifier is
considered immutable and a syntax error is raised.

@examples[#:eval the-eval
(define the-box (box add1))
(define-syntax op
  (make-variable-like-transformer
   #'(unbox the-box)
   #'(lambda (v) (set-box! the-box v))))
(op 5)
(set! op 0)
op
]

@history[#:added "6.3"]{}
}

@close-eval[the-eval]