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Trying out the first example in the book<br><br>#lang plai<br>(define (parse sexp)<br> (cond<br> [(number? sexp) (num sexp)]<br> [(list? sexp)<br> (case (first sexp)<br> [(+) (add (parse (second sexp))<br> (parse (third sexp)))]<br> [(-) (sub (parse (second sexp))<br> (parse (third sexp)))])]))<br><br>I get <br><br><unsaved editor>:4:21: expand: unbound identifier in module in: num<br><br>FWIW I have installed the patch on the books webpage and am running Racket 5.01 on Ubuntu.<br> </body>
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