Hi,
I'm trying to implement arc as a racket language extension. To become
familiar with racket's reader infrastructure, I thought I'd start with
something simple:
==================
kogir/arc/lang/reader.rkt:
==================
#lang s-exp syntax/module-reader
(planet kogir/arc/language)
#:wrapper1 arc-read-wrapper
(require (planet kogir/arc/reader))
==============
kogir/arc/reader.rkt:
==============
#lang racket/base
(provide make-arc-readtable
arc-read-wrapper)
(define (read-square-brackets ch port src line col pos)
(datum->syntax
#f
`(lambda (_)
,(read-syntax/recursive src port #\[ #f))
(let-values ([(l c p) (port-next-location port)])
(list src line col pos (and pos (- p pos))))))
(define (make-arc-readtable)
(make-readtable (current-readtable)
#\[ 'terminating-macro read-square-brackets))
(define (arc-read-wrapper thunk read-syntax)
(parameterize ([current-readtable (make-arc-readtable)])
(thunk)))
================
kogir/arc/language.rkt:
================
#lang racket
(provide (all-defined-out)
(all-from-out racket))
I expected it to give me a language very similar to racket, but with
arc's [ _ ] lambda syntax sugar:
[+ _ 1] => (lambda (_) (+ _ 1))
When I test in Dr. Racket, it works for reading files, but not in the
interaction window:
======
test.arc:
======
#lang planet kogir/arc
(define test [+ _ 1])
---------------------------------------------------------------------------------------
Welcome to DrRacket, version 5.2.1 [3m].
Language: planet kogir/arc [custom]; memory limit: 128 MB.
> test
#<procedure:test>
> (test 1)
2
> [+ _ 1]
. _: wildcard not allowed as an expression in: _
What pieces am I missing to make the Dr. Racket interaction window
support the new syntax?
Also, is it correct in kogir/arc/reader.rkt to use
`(lambda (_)
,(read-syntax/recursive src port #\[ #f)
or should I use
#`(lambda (_)
#,(read-syntax/recursive src port #\[ #f)
Both appear to work?
Any pointers you might have would be awesome. I apologize in advance
if I missed something obvious.
Thanks,
Nick
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