Learning Racket #2: Macros, Macros and a Bit of Modules

by mmastrac • 12 years ago

113 5 12 years ago

gus_massa• 12 years ago

Just nitpicking. The first example that uses define-syntax-rule can also be fixed with “...”. He uses the “...” later in syntax-parse, but they are available in define-syntax-rule too. With syntax-parse is easier to construct advanced macros, but I like to use define-syntax-rule for small throwaway macros.

  #lang racket
  
  (define-syntax-rule (def id body ...) (define id body ...))
  
  (def (vector-swap! vec i j)
    (def t (vector-ref vec i))
    (vector-set! vec i (vector-ref vec j))
    (vector-set! vec j t))
  
  (let ([v (vector 'a 'b 'c)])
    (vector-swap! v 0 1)
    v)  ;==> (vector 'b 'a 'c)

artyomkazak• 12 years ago

Thanks for telling! (I've written a bit of a response here: http://artyom.me/learning-racket-2#gus_massa-from-hn .)

e12e• 12 years ago

While I know hn discourages "mee too!"-posts, let me just say that I find these series really interesting. I'm such a lazy programmer, I just love having someone else muck about with stuff like this macro-madness and then tell me about it, saving me from having to start up racket at all :-)

In short: Keep at it! It's greatly appreciated.

dang• 12 years ago

HN discourages substanceless comments, but this one is just fine.

minikomi• 12 years ago

    I'm afraid that with the level of flexibility Racket allows, I'll never get to writing an actual program

Great series

Learning Racket #2: Macros, Macros and a Bit of Modules

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