Parallel assignment

[cameyo]

Hi all,

this is my first macro to do parallel assignment:

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(define-macro (psetq)
  (let ((_var '()) (_ex '()))
    ; for each expression in (args 1) ...
    (for (i 0 (- (length (args 1)) 1))
      ; expand the i-th expression with the value
      ; of each variable in (args 0)
      (setq _ex (expand (args 1 i) (args 0 0)))
      ; loop that expands the i-th expression for each variable
      (for (j 1 (- (length (args 0)) 1))
        (setq _ex (expand _ex (args 0 j)))
        (println _ex)
      )
      ; adds the expanded expression to a list
      (push _ex _var -1)
    )
    (println _var)
    ; assigns to each variable the evaluation
    ; of the relative expression of the created list
    (dolist (el _var)
      (set (args 0 $idx) (eval el))
    )
  )
)
Examples:
(setq x 2 y 3)
(psetq (x y) ((+ 1 y) (+ 1 x)))
;-> (+ 1 3)
;-> (+ 1 2)
;-> ((+ 1 3) (+ 1 2))
(list x y)
;-> (4 3)

(setq x 1)
(setq y 2)
(setq z 3)
(psetq (x y z) ((+ x y z) (- z y x) (- x y z)))
;-> (+ 1 2 z)
;-> (+ 1 2 3)
;-> (- z 2 1)
;-> (- 3 2 1)
;-> (- 1 2 z)
;-> (- 1 2 3)
;-> ((+ 1 2 3) (- 3 2 1) (- 1 2 3))
(list x y z)
;-> (6 0 -4)
Does anyone have any advice to improve it?

cameyo

p.s. thank you all for reactivating the forum

[newBert]

Just another way to do it (with what comes to hand):

Code Select Expand

> (setq x 2 y 3)
3
> (map set '(x y) (list (+ 1 y) (+ 1 x)))
(4 3)

> (setq x 1 y 2 z 3)
3
> (map set '(x y z) (list (+ x y z) (- z y x) (- x y z)))
(6 0 -4)
 

:)

[cameyo]

Thanks !

I suspected that the map function could have been useful... :-)

[newBert]

Yes, map is a very useful function which works well in parallel.

It is handy too to take the place of 'list comprehensions'...