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Quick bad-macro example.

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Eli Barzilay 2013-07-16 04:17:43 -04:00
parent 0063574a4d
commit d97565efa1
1 changed files with 9 additions and 1 deletions
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10
racket.html.markdown
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@ -353,7 +353,7 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) <-- no `d'
(for ([i (in-range 5 10)])
(printf "i=~a\n" i)) ; => i=5, i=6, ...
;;; Other Sequences
;;; Iteration Over Other Sequences
;; `for' allows iteration over many other kinds of sequences:
;; lists, vectors, strings, sets, hash tables, etc...
@ -557,6 +557,14 @@ vec ; => #(1 2 3 4)
(swap! a b)
(printf "tmp = ~a; a = ~a; b = ~a\n" tmp a b) ; tmp is unaffected
;; But the are still code transformations, for example:
(define-syntax-rule (bad-while condition body ...)
(when condition
body ...
(bad-while condition body ...)))
;; this macro is broken: it generates infinite code, if you try to use
;; it, the compiler will get in an infinite loop
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 10. Contracts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;