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- LISP - notevery function
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Lisp - Logical Operators
Common LISP provides three logical operators: and, or, and not that operates on Boolean values. Assume A has value nil and B has value 5, then −
| Operator | Description | Example |
|---|---|---|
| and | It takes any number of arguments. The arguments are evaluated left to right. If all arguments evaluate to non-nil, then the value of the last argument is returned. Otherwise nil is returned. | (and A B) will return NIL. |
| or | It takes any number of arguments. The arguments are evaluated left to right until one evaluates to non-nil, in such case the argument value is returned, otherwise it returns nil. | (or A B) will return 5. |
| not | It takes one argument and returns t if the argument evaluates to nil. | (not A) will return T. |
Example - and Operator
Create a new source code file named main.lisp and type the following code in it. Here we're using and operator to check various scenarios.
main.lisp
; set a as 10 (setq a 10) ; set b as 20 (setq b 20) ; perform and operation on a and b (format t "~% A and B is ~a" (and a b)) ; terminate printing (terpri) ; set a as nil (setq a nil) ; set b as 5 (setq b 5) ; perform and operation on a and b (format t "~% A and B is ~a" (and a b)) ; terminate printing (terpri) ; set a as nil (setq a nil) ; set b as 0 (setq b 0) ; perform and operation on a and b (format t "~% A and B is ~a" (and a b)) ; terminate printing (terpri) ; set values to variables (setq a 10) (setq b 0) (setq c 30) (setq d 40) ; print and operation on all four variables (format t "~% Result of and operation on 10, 0, 30, 40 is ~a" (and a b c d)) ; terminate printing (terpri) ; set values to variables (setq a 10) (setq b 20) (setq c nil) (setq d 40) ; print and operation on all four variables (format t "~% Result of and operation on 10, 20, nil, 40 is ~a" (and a b c d))
Output
When you click the Execute button, or type Ctrl+E, LISP executes it immediately and the result returned is −
A and B is 20 A and B is NIL A and B is NIL Result of and operation on 10, 0, 30, 40 is 40 Result of and operation on 10, 20, nil, 40 is NIL
Example - or Operator
Update the source code file named main.lisp and type the following code in it. Here we're using or operator to check various scenarios.
main.lisp
; set a as 10 (setq a 10) ; set b as 20 (setq b 20) ; print or operation on a and b (format t "~% A or B is ~a" (or a b)) ; terminate printing (terpri) ; set a as nil (setq a nil) ; set b as 5 (setq b 5) ; perform or operation on a and b (format t "~% A or B is ~a" (or a b)) ; terminate printing (terpri) ; set a as nil (setq a nil) ; set b as 0 (setq b 0) ; perform or operation on a and b (format t "~% A or B is ~a" (or a b)) ; terminate printing (terpri) ; set values of variables (setq a 10) (setq b 0) (setq c 30) (setq d 40) ; perform or operation on variables (format t "~% Result of and operation on 10, 0, 30, 40 is ~a" (or a b c d)) ; terminate printing (terpri) ; set values of variables (setq a 10) (setq b 20) (setq c nil) (setq d 40) ; perform or operation on variables (format t "~% Result of and operation on 10, 20, nil, 40 is ~a" (or a b c d))
Output
When you click the Execute button, or type Ctrl+E, LISP executes it immediately and the result returned is −
A or B is 10 A or B is 5 A or B is 0 Result of and operation on 10, 0, 30, 40 is 10 Result of and operation on 10, 20, nil, 40 is 10
Example - not Operator
Update the source code file named main.lisp and type the following code in it. Here we're using not operator to check various scenarios.
main.lisp
; set a as 10 (setq a 10) ; perform not operation on a (format t "~% not A is ~a" (not a)) ; terminate printing (terpri) ; set q as nil (setq a nil) ; perform not operation on a (format t "~% not A is ~a" (not a)) ; terminate printing (terpri) ; set q as 0 (setq a 0) ; perform not operation on a (format t "~% not A is ~a" (not a))
Output
When you click the Execute button, or type Ctrl+E, LISP executes it immediately and the result returned is −
not A is NIL not A is T not A is NIL
Please note that the logical operations work on Boolean values and secondly, numeric zero and NIL are not same.
lisp_operators.htm
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