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mem                                                              (Lib)
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mem : ''a -> ''a list -> bool

SYNOPSIS
Tests whether a list contains a certain member.

KEYWORDS
list, set, eqtype.

LIBRARY
Lib

DESCRIBE
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}.

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

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