Function: -setq

-setq is a macro defined in dash.el.

Signature

(-setq [MATCH-FORM VAL]...)

Documentation

Bind each MATCH-FORM to the value of its VAL.

MATCH-FORM destructuring is done according to the rules of -let.

This macro allows you to bind multiple variables by destructuring the value, so for example:

  (-setq (a b) x
         (&plist :c c) plist)

expands roughly speaking to the following code

  (setq a (car x)
        b (cadr x)
        c (plist-get plist :c))

Care is taken to only evaluate each VAL once so that in case of multiple assignments it does not cause unexpected side effects.

View in manual

Source Code

;; Defined in ~/.emacs.d/elpa/dash-20260221.1346/dash.el
(defmacro -setq (&rest forms)
  "Bind each MATCH-FORM to the value of its VAL.

MATCH-FORM destructuring is done according to the rules of `-let'.

This macro allows you to bind multiple variables by destructuring
the value, so for example:

  (-setq (a b) x
         (&plist :c c) plist)

expands roughly speaking to the following code

  (setq a (car x)
        b (cadr x)
        c (plist-get plist :c))

Care is taken to only evaluate each VAL once so that in case of
multiple assignments it does not cause unexpected side effects.

\(fn [MATCH-FORM VAL]...)"
  (declare (debug (&rest sexp form))
           (indent 1))
  (when (= (mod (length forms) 2) 1)
    (signal 'wrong-number-of-arguments (list '-setq (1+ (length forms)))))
  (let* ((forms-and-sources
          ;; First get all the necessary mappings with all the
          ;; intermediate bindings.
          (-map (lambda (x) (dash--match (car x) (cadr x)))
                (-partition 2 forms)))
         ;; To preserve the logic of dynamic scoping we must ensure
         ;; that we `setq' the variables outside of the `let*' form
         ;; which holds the destructured intermediate values.  For
         ;; this we generate for each variable a placeholder which is
         ;; bound to (lexically) the result of the destructuring.
         ;; Then outside of the helper `let*' form we bind all the
         ;; original variables to their respective placeholders.
         ;; TODO: There is a lot of room for possible optimization,
         ;; for start playing with `special-variable-p' to eliminate
         ;; unnecessary re-binding.
         (variables-to-placeholders
          (-mapcat
           (lambda (bindings)
             (-map
              (lambda (binding)
                (let ((var (car binding)))
                  (list var (make-symbol (concat "--dash-binding-" (symbol-name var) "--")))))
              (--filter (not (string-prefix-p "--" (symbol-name (car it)))) bindings)))
           forms-and-sources)))
    `(let ,(-map 'cadr variables-to-placeholders)
       (let* ,(-flatten-n 1 forms-and-sources)
         (setq ,@(-flatten (-map 'reverse variables-to-placeholders))))
       (setq ,@(-flatten variables-to-placeholders)))))