LISP - notany function

Lisp - The notany Function

The notany function is a sequence predicate that determines if a given test is false for every element in a sequence. It is the logical negation of the some function. You can think of notany as asking the question: “Is there no element that satisfies this condition?”

Syntax

(notany predicate sequence &rest more-sequences)

Arguments

• predicate: A function designator (e.g., a function name or a lambda function) that accepts one argument per sequence.
• sequence: The primary sequence to test. This can be a list, a vector, or a string.
• more-sequences: Optional additional sequences. If provided, the predicate must accept a number of arguments equal to the total number of sequences.

Return Value

Returns T (true) if the predicate returns NIL (false) for every element. If the predicate returns a non-NIL value for any element, notany immediately stops and returns NIL.

Example 1: Basic Check for Even Numbers

Let’s check if a list contains any even numbers.

;; The predicate is #'evenp.
;; Is it true that NO element is even?

;; Returns T because no number in the list is even.
(notany #'evenp '(1 3 5 7 9))
; => T

;; Returns NIL because 2 is even, so the condition "no element is even" is false.
(notany #'evenp '(1 2 3 5 7 9))
; => NIL

Example 2: Using a lambda for a Custom Predicate

We can use an anonymous lambda function to perform custom checks, such as finding if any number is greater than 10.

;; Predicate: a lambda checking if a number is greater than 10.
(defvar *my-numbers* '(1 15 4 2))

;; Is it true that NO number is greater than 10?
;; Returns NIL because 15 > 10.
(notany #'(lambda (x) (> x 10)) *my-numbers*)
; => NIL

;; Is it true that NO number is greater than 20?
;; Returns T because all numbers are <= 20.
(notany #'(lambda (x) (> x 20)) *my-numbers*)
; => T

Example 3: Working with Strings

Sequences can also be strings. Here, we check if a string contains any numeric digits.

;; The predicate #'digit-char-p checks if a character is a digit.

;; Is it true that NO character is a digit?
;; Returns T because the string contains only letters.
(notany #'digit-char-p "TutorialsPoint")
; => T

;; Returns NIL because '1' is a digit.
(notany #'digit-char-p "Lisp-101")
; => NIL

Example 4: Using Multiple Sequences

When using multiple sequences, the predicate must accept one argument from each sequence.

;; Predicate: #'> (greater than)
;; Checks if any element from the first list is greater than the
;; corresponding element from the second list.

;; Is it true that NO element from list1 is greater than its counterpart in list2?
;; Returns NIL because 3 > 2.
(notany #'> '(1 2 3) '(4 1 2))
; => NIL

;; Returns T because in every pair (1 4), (2 5), (3 6), the first element is not greater.
(notany #'> '(1 2 3) '(4 5 6))
; => T

Common Applications and Debugging

• Data Validation: Quickly verify that a collection of inputs contains no invalid values (e.g., (notany #'is-invalid-p user-inputs)).
• State Verification: Ensure a system is in a safe state by checking that no component has an error flag (e.g., (notany #'has-error-p *system-components*)).
• Set Operations: Check if two sets are disjoint (have no elements in common).
• Debugging Tip: Remember that notany on an empty sequence () will always return T, because the condition “the predicate is true for an element” is never met.