multiple-value-setq

ToC

Allegro CL

ANSI Common Lisp

5 Data and Control Flow

5.3 Dictionary of Data and Control Flow

5.3.52 multiple-value-setq

Macro

Syntax:

multiple-value-setq vars form

result

Arguments and Values:

vars - a list of symbols that are either variable names or names of symbol macros.

form - a form.

result - The primary value returned by the form.

Description:

multiple-value-setq assigns values to vars.

The form is evaluated, and each var is assigned to the corresponding value returned by that form. If there are more vars than values returned, nil is assigned to the extra vars. If there are more values than vars, the extra values are discarded.

If any var is the name of a symbol macro, then it is assigned as if by setf. Specifically,

 (multiple-value-setq (symbol₁ ... symbol_N) value-producing-form)

is defined to always behave in the same way as

 (values (setf (values symbol₁ ... symbol_N) value-producing-form))

in order that the rules for order of evaluation and side-effects be consistent with those used by setf. See Section 5.1.2.3 VALUES Forms as Places.

Examples:

 (multiple-value-setq (quotient remainder) (truncate 3.2 2))  1
 quotient  1
 remainder  1.2
 (multiple-value-setq (a b c) (values 1 2))  1
 a  1
 b  2
 c   NIL
 (multiple-value-setq (a b) (values 4 5 6))  4
 a  4
 b  5

See Also:

setq, symbol-macrolet

Allegro CL Implementation Details:

None.