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Beau­tiful Racket / tuto­rials

Go with the flow: basic

With the tokenizer and the parser complete, our reader will follow the pattern we’ve used before:

basic/main.rkt
#lang br/quicklang
(require "parser.rkt" "tokenizer.rkt")

(define (read-syntax path port)
  (define parse-tree (parse path (make-tokenizer port path)))
  (strip-bindings
   #`(module basic-mod basic/expander
       #,parse-tree)))

(module+ reader
  (provide read-syntax)) 
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#lang br/quicklang
(require "parser.rkt" "tokenizer.rkt")

(define (read-syntax path port)
  (define parse-tree (parse path (make-tokenizer port path)))
  (strip-bindings
   #`(module basic-mod basic/expander
       #,parse-tree)))

(module+ reader
  (provide read-syntax))
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None of this is new mate­rial.

First, we make a parse tree. We call make-tokenizer with our input port. This time, we also pass our path as an argu­ment, to help with gener­ating source loca­tions. make-tokenizer returns a token-retrieving func­tion, which we pass to parse. In turn, the parser uses this func­tion to retrieve tokens and arrange them into a parse tree according to the rules of our grammar.

To insert the parse tree into our module expres­sion, we use the quasi­syntax nota­tion we used for the wires reader. We wrap this new module expres­sion with strip-bindings to make sure it has no bind­ings before it’s passed to the expander.

Finally, we provide our read-syntax func­tion through a reader submodule, where Racket will look for it when we invoke #lang basic.

Now we’re ready to start the expander.

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