:: Eq a => [a] -> a -> Bool -package:base package:hledger-web

Does the element occur in the structure? Note: elem is often used in infix form.

Examples

Basic usage:
>>> 3 `elem` []
False
>>> 3 `elem` [1,2]
False
>>> 3 `elem` [1,2,3,4,5]
True
For infinite structures, the default implementation of elem terminates if the sought-after value exists at a finite distance from the left side of the structure:
>>> 3 `elem` [1..]
True
>>> 3 `elem` ([4..] ++ [3])
* Hangs forever *
notElem is the negation of elem.

Examples

Basic usage:
>>> 3 `notElem` []
True
>>> 3 `notElem` [1,2]
True
>>> 3 `notElem` [1,2,3,4,5]
False
For infinite structures, notElem terminates if the value exists at a finite distance from the left side of the structure:
>>> 3 `notElem` [1..]
False
>>> 3 `notElem` ([4..] ++ [3])
* Hangs forever *