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is_exists1                                                (boolSyntax)
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is_exists1 : term -> bool

SYNOPSIS
Tests a term to see if it is a unique existence term.

DESCRIBE
If {M} has the form {?!v. t} then {is_exists1 M} returns {true}.
If the term is not a unique existence quantification the result is {false}.

FAILURE
Never fails.

SEEALSO
boolSyntax.mk_exists1, boolSyntax.dest_exists.

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