[plt-scheme] how to get rid of eval ; was : how to quote identifier in macro

From: Andre Mayers (andre.mayers at usherbrooke.ca)
Date: Thu Dec 11 20:56:41 EST 2008

It almost works. I don’t know how to insert the binding inside de let


(define attr '(a1 a2 a3))


(define slot-value

  (λ (slot-name objet)

    (cadr (assq slot-name objet))))


(define-syntax (tata stx)

  (syntax-case stx ()

    [(_ a v (s ps ...) body ...)

     #'(λ (self ps ...) 

           `(let ,(map (λ (p-attr) 

                        (list p-attr 

                         (slot-value p-attr self)))


                 body ...))



 ((tata attr vals (self p1 p2) (display self) (newline) (+ p2 a1))  

 '((a1 10)(a2 20)(a3 30)) 4 5)



(let ((a1 10) (a2 20) (a3 30)) (display self) (newline) (+ p2 a1))


If I remove the quote in front of the let, I got the following  error

let: bad syntax (not an identifier and expression for a binding) in: map


De : YC [mailto:yinso.chen at gmail.com] 
Envoyé : December-11-08 7:29 PM
À : andre.mayers at usherbrooke.ca
Cc : pltscheme
Objet : Re: [plt-scheme] how to quote identifier in macro



On Thu, Dec 11, 2008 at 3:32 PM, Andre Mayers <andre.mayers at usherbrooke.ca> wrote:

Eureka. It works. 

Now how to get rid of eval ?

As Noel said, try to write what you want as the final result, instead of using list & list* to create the expression and then eval it.

As an example, the following creates a lambda without list, list*, and eval.

(define-syntax (tada2 stx)
  (syntax-case stx ()
    ((_ a1 a2 ...)
     #'(lambda (a1 a2 ...)
         (list a1 a2 ... 'a1 'a2 ...)))))

((tada2 a b c) 1 2 3) ;; => ??


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