Association Lists

Association lists store (functional) binary relations.

Lisp functions ACONS and ASSOC help.

> (setq fruit-colors nil)

NIL

> (setq fruit-colors (acons 'apple 'red fruit-colors))

((APPLE . RED))

> (setq fruit-colors (acons 'pear ’green fruit-colors))

((PEAR . GREEN)(APPLE . RED))

> (assoc 'apple fruit-colors)

(APPLE . RED)

> (assoc 'banana fruit-colors)

NIL

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