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

LIBRARY
Lib

SYNOPSIS
Tests whether a list contains a certain element.

KEYWORDS
list, set.

DESCRIBE
An invocation {op_mem eq x [x1,...,xn]} returns {true} if, for
some {xi} in the list, {eq xi x} evaluates to {true}.
Otherwise it returns {false}.

FAILURE
Only fails if an application of {eq} fails.

EXAMPLE

- op_mem aconv (Term `\x. x /\ y`) [T, Term `\z. z /\ y`, F];
> val it = true : bool




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

SEEALSO
Lib.mem, Lib.op_insert, Lib.tryfind, Lib.exists, Lib.all, Lib.assoc,
Lib.rev_assoc, Lib.assoc1, Lib.assoc2, Lib.op_union, Lib.op_mk_set,
Lib.op_U, Lib.op_intersect, Lib.op_set_diff.

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