mem

Lib.mem : ''a -> ''a list -> bool

Tests whether a list contains a certain member.

An invocation mem x [x1,...,xn] returns true if some xi in the list is equal to x. Otherwise it returns false.

Failure

Never fails.

Comments

Note that the type of the members of the list must be an SML equality type. If set operations on a non-equality type are desired, use the ‘op_’ variants, which take an equality predicate as an extra argument.

A high-performance implementation of finite sets may be found in structure HOLset.

See also

Lib.op_mem, Lib.insert, Lib.tryfind, Lib.exists, Lib.all, Lib.assoc, Lib.rev_assoc