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)
[(_ id:id expr) (begin
(if (duplicate-exists? id)
(syntax-error "Oh no!")
#'(define id expr)]))
I know there's a lot of functions like bound-identifier=? and
check-duplicate-identifier, but they seem to all be geared towards the user
putting in all the identifiers in question as function arguments. In this case,
I need a function like
that just takes in the single identifier, and checks to see if, in the scope
the function is invoked, there's a duplicate identifier already there. I just
can't seem to figure out how to write that function.
Thanks in advance!
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