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Macro

push

push item place ⇒ new-place-value

Arguments and Values

iteman object.
placea place, the value of which may be any object.
new-place-valuea list (the new value of place).

Description

push prepends item to the list that is stored in place, stores the resulting list in place, and returns the list.

For information about the evaluation of subforms of place, see Evaluation of Subforms to Places.

Examples

 (setq llst '(nil)) ⇒  (NIL)
 (push 1 (car llst)) ⇒  (1)
 llst ⇒  ((1))
 (push 1 (car llst)) ⇒  (1 1)
 llst ⇒  ((1 1))
 (setq x '(a (b c) d)) ⇒  (A (B C) D)
 (push 5 (cadr x)) ⇒  (5 B C)  
 x ⇒  (A (5 B C) D)

Side Effects

The contents of place are modified.

See Also

pop, pushnew, Generalized Reference

Notes

The effect of (push item place) is equivalent to 

 (setf place (cons item place))

except that the subforms of place are evaluated only once, and item is evaluated before place.

Backlinks

Conses as Lists, Conses Dictionary, Evaluation of Subforms to Places, Examples of Evaluation of Subforms to Places, getf, Overview of Places and Generalized Reference, pop, pushnew, Symbols in the COMMON-LISP Package, Treatment of Other Macros Based on SETF