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is_neg                                                    (boolSyntax)
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is_neg : term -> bool

SYNOPSIS
Tests a term to see if it is a negation.

DESCRIBE
If {M} has the form {~t}, then {is_neg M} returns {true}.
If the term is not a negation the result is {false}.

FAILURE
Never fails.

SEEALSO
boolSyntax.mk_neg, boolSyntax.dest_neg.

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