Learning Racket #2: Macros, Macros and a Bit of Modules(artyom.me)

113 pointsby mmastrac12 anni fa5 comments

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

http://artyom.me/learning-racket-2

6 comments

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)

artyomkazak12 anni fa

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

[deleted]12 anni fa

minikomi12 anni fa

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

Great series

e12e12 anni fa

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.

dang12 anni fa

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