ch2_1_defconstant
DEFCONSTANT
Define symbol in global scope as constant. Constant symbol cannot be overwritten by SETQ, and cannot be even used as local variable in LET.
DEFCONSTANT form needs two arguments, and can have one more optional description string. The first parameter must be a symbol. Symbols from base package (reserved) will not be allowed, but DEFCONSTANT can be used to overwrite the value of user-defined constant. Second argument is evaluated, and will be bound as the value for the constant. Third, optional argument is a description string.
>(defconstant eul 2.72 "euler's number") ; defining new meaningful constant EUL >(defconstant pi 3.14) ; trying to redefine built-in PI ;Using base-package name for DEFCONSTANT. Not allowed. ; it fails NIL >(defconstant eul 2.71828) ; redefine with better precision EUL
See also: DEFPARAMETER, DEFVAR, SETQ
ch2_1_defconstant.txt · Last modified: 2022/02/25 00:36 by admin