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progv Data and Control Flow Dictionary psetq
Special Operator

setq

setq {!pair}* ⇒ result

pair ::=var form

Pronunciation

pronounced ’set ,ky\"u

Arguments and Values

vara symbol naming a variable other than a constant variable.
forma form.
resultthe primary value of the last form, or nil if no pairs were supplied.

Description

Assigns values to variables.

(setq var1 form1 var2 form2 ...) is the simple variable assignment statement of Lisp. First form1 is evaluated and the result is stored in the variable var1, then form2 is evaluated and the result stored in var2, and so forth. setq may be used for assignment of both lexical and dynamic variables.

If any var refers to a binding made by symbol-macrolet, then that var is treated as if setf (not setq) had been used.

Examples

 ;; A simple use of SETQ to establish values for variables.
 (setq a 1 b 2 c 3) ⇒  3
 a ⇒  1
 b ⇒  2
 c ⇒  3

 ;; Use of SETQ to update values by sequential assignment.
 (setq a (1+ b) b (1+ a) c (+ a b)) ⇒  7
 a ⇒  3
 b ⇒  4
 c ⇒  7

 ;; This illustrates the use of SETQ on a symbol macro.
 (let ((x (list 10 20 30)))
   (symbol-macrolet ((y (car x)) (z (cadr x)))
     (setq y (1+ z) z (1+ y))
     (list x y z)))
⇒  ((21 22 30) 21 22)

Side Effects

The primary value of each form is assigned to the corresponding var.

See Also

psetq, set, setf; psetf

Errata

This section lists errata in the ANSI standard that have been amended in this CLCS entry.

  • The title for setq is given as "Special Form SETQ" instead of "Special Operator SETQ".

Backlinks

boundp, call-next-method, Closures and Lexical Binding, Data and Control Flow Dictionary, define-method-combination, define-symbol-macro, do, do*, Expanding Loop Forms, multiple-value-setq, psetq, set, Special Forms, symbol-macrolet, symbol-value, Symbols as Forms, Symbols in the COMMON-LISP Package, type, with-accessors, with-slots