memberchk/2

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.^{136Eventually
here means it will scan as many elements as the longest list that may
exist given the current stack usage before raising the exception.}