Lisp - Comparison Predicates

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Lisp provides various useful comparison predicates which tests for a condition and return t as true and nil as false. These predicates are mainly useful for decision making and control flow statements like cond, if, when and unless statements. These predicates can be treated as operators as well.

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

Example < Predicate

Following code check if first number is less than second number.

main.lisp

(write(< 5 3))        ; NIL
(terpri)
(write(< 3 5))        ; T

Output

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

NIL
T

Example > Predicate

Following code check if first number is greater than second number.

main.lisp

(write(> 5 3))        ; T
(terpri)
(write(> 3 5))        ; NIL

Output

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

T
NIL

Example <= Predicate

Following code check if first number is less than second number.

main.lisp

(write(<= 5 3))        ; NIL
(terpri)
(write(<= 3 5))        ; T
(terpri)
(write(<= 5 5))        ; T

Output

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

NIL
T
T

Example >= Predicate

Following code check if first number is greater than second number.

main.lisp

(write(>= 5 3))        ; T
(terpri)
(write(>= 3 5))        ; NIL
(terpri)
(write(>= 5 5))        ; T

Output

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

T
NIL
T

Example = Predicate

Following code check if first number is equal to second number.

main.lisp

(write(= 5 3))        ; NIL
(terpri)
(write(= 5 5))        ; T

Output

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

NIL
T