chickadee » lookup-table » dict-update!

dict-update! DICT KEY DEF-VAL-PROCEDURE #!optional FUNCprocedure

Invokes FUNC on either the existing value for KEY in the DICT, or the result of the DEF-VAL-PROCEDURE when no existing value. The result then becomes the value for KEY in the DICT.

Returns the updated value for KEY in the DICT.

FUNC
(* -> *) ; identity

DEF-VAL-PROCEDURE must not return (void)!