Lisp - Numeric Predicates

Quiz

Lisp provides various useful numeric predicates which can be used to compare number for specific functionality.

The following table shows some of the most commonly used numeric predicates −

Sr.No.	Predicate & Description
1	evenp It takes one numeric argument and returns t if the argument is even number or nil if otherwise.
2	oddp It takes one numeric argument and returns t if the argument is odd number or nil if otherwise.
3	zerop It takes one numeric argument and returns t if the argument is zero or nil if otherwise.
4	plusp It takes one numeric argument and returns t if the argument is positive if otherwise.
5	minus It takes one numeric argument and returns t if the argument is negative if otherwise.

Example - evenp

Following code check if given number is an even number.

(write(evenp 100))        ; T
(terpri)
(write(evenp 101))        ; NIL

When you execute the code, it returns the following result −

T
NIL

Following code check if given number is an odd number.

(write(oddp 100))        ; NIL
(terpri)
(write(oddp 101))        ; T

When you execute the code, it returns the following result −

NIL
T

Following code check if given number is zero.

(write(zerop 0))         ; T
(terpri)
(write(zerop 101))       ; NIL

When you execute the code, it returns the following result −

T
NIL

Following code check if given number is a positive number.

(write(plusp 0))         ; NIL
(terpri)
(write(plusp 101))       ; T
(terpri)
(write(plusp -101))      ; NIL

When you execute the code, it returns the following result −

NIL
T
NIL

Following code check if given number is a negative number.

(write(minusp 0))         ; NIL
(terpri)
(write(minusp 101))       ; NIL
(terpri)
(write(minusp -101))      ; T

When you execute the code, it returns the following result −

NIL
NIL
T

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