• MemberQ[list, form] returns True if an element of list matches form, and False otherwise.
• MemberQ[list, form, levelspec] tests all parts of list specified by levelspec.
• form can be a pattern.
• The first argument of MemberQ
can have any head, not necessarily List
• MemberQ[list, form] immediately tests whether any expression in list matches form; Element[x, dom] asserts that x is an element of the symbolic domain dom.
• New in Version 1.