[racket] Reading Graph Structure: read: #..= expressions not allowed in read-syntax mode (??)

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Hi,

why does the following code


#lang racket

(struct _dl (left val right))

(define (dlist a b c)
  #1=(_dl #f a #2=(_dl #1# b (_dl #2# c #f))) )


produce the error:

Module Language: invalid module text
. read: #..= expressions not allowed in read-syntax mode

Marijn
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