memberchk/2

Documentation
- Reference manual
  - Built-in Predicates
    - Built-in list operations
      - is_list/1
      - memberchk/2
      - length/2
      - sort/2
      - sort/4
      - msort/2
      - keysort/2
      - predsort/3
- Packages

Availability:built-in

[semidet]memberchk(?Elem, +List)

True when Elem is an element of List. This‘chk’variant of member/2 is semi deterministic and typically used to test membership of a list. Raises a type error if scanning List encounters a non-list. Note that memberchk/2 does not perform a full list typecheck. For example,

memberchk(a, 
[a|b])

succeeds without error. If List is cyclic and Elem is not a member of List, memberchk/2 eventually raises a type error.^{139Eventually
here means it will scan as many elements as the longest list that may
exist given the current stack usage before raising the exception.}