destructuring-bind

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ANSI Common Lisp 5 Data and Control Flow 5.3 Dictionary of Data and Control Flow

5.3.17 destructuring-bind Macro

Syntax:

destructuring-bind lambda-list expression {declaration}* {form}*
{result}*

Arguments and Values:

lambda-list - a destructuring lambda list.

expression - a form.

declaration - a declare expression; not evaluated.

forms - an implicit progn.

results - the values returned by the forms.

Description:

destructuring-bind binds the variables specified in lambda-list to the corresponding values in the tree structure resulting from the evaluation of expression; then destructuring-bind evaluates forms.

The lambda-list supports destructuring as described in Section 3.4.5 Destructuring Lambda Lists.

Examples:

 (defun iota (n) (loop for i from 1 to n collect i)) ;helper
 (destructuring-bind ((a &optional (b 'bee)) one two three)
 `((alpha) ,@(iota 3))
 (list a b three two one)) (ALPHA BEE 3 2 1)

Exceptional Situations:

If the result of evaluating the expression does not match the destructuring pattern, an error of type error should be signaled.

See Also:

macrolet, defmacro

Allegro CL Implementation Details:

None.

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