To take care of shadowing you need to keep track of which identifiers are
declared in each internal definition context.
Here is one way to do it.
/Jens Axel
#lang racket
;;;
;;; Declarations
;;;
;; This is a demonstration of how to write a declaration (or definition)
;; form, that can raise a sy
Why don’t you intercept the exception in the error handler and rewrite the
error message? Racket already disallows duplicate names in the same scope,
which seems to be what you want, except that you don’t like the way the errors
are reported.
> On Jul 18, 2017, at 5:47 PM, Sam Waxman wrote
Thanks both for your replies, but it doesn't look like either of these will do
exactly what I want. While the code keeping track of id's that you wrote comes
close, it doesn't allow for shadowing. I still want racket to do everything
that it used to do, so the program
(define a 3)
(let ()
(d
#lang racket
(require (for-syntax syntax/parse syntax/id-set))
(begin-for-syntax
(define defined-ids (mutable-free-id-set))
(define (already-defined? x) (free-id-set-member? defined-ids x))
(define (define-it! x) (free-id-set-add!defined-ids x)))
(define-syntax (def stx)
#lang racket
(define my-favorite-numbers '(1 2 3))
(define (duplicate-exists? n)
(member n my-favorite-numbers))
(duplicate-exists? 3)
(duplicate-exists? 4)
> On Jul 17, 2017, at 3:43 AM, Sam Waxman wrote:
>
> Hello,
>
> In the regular #racket, the following program
>
> (define a 1)
Hello,
In the regular #racket, the following program
(define a 1)
(define a 2)
will result in a syntax error letting you know that you have a duplicate
identifier. I would like to make my own define that throws a custom error
message in this case. I.e.
(define-syntax (my-define stx)
(syntax
6 matches
Mail list logo
