\DOC PSELECT_CONV
\TYPE {PSELECT_CONV : conv}
\KEYWORDS
conversion, epsilon.
\LIBRARY pair
\SYNOPSIS
Eliminates a paired epsilon term by introducing a existential quantifier.
\DESCRIBE
The conversion {PSELECT_CONV} expects a boolean term of the form
{"t[@p.t[p]/p]"}, which asserts that the epsilon term {@p.t[p]} denotes
a pair, {p} say, for which {t[p]} holds. This assertion is equivalent
to saying that there exists such a pair, and {PSELECT_CONV} applied to a
term of this form returns the theorem {|- t[@p.t[p]/p] = ?p. t[p]}.
\FAILURE
Fails if applied to a term that is not of the form {"p[@p.t[p]/p]"}.
\SEEALSO
SELECT_CONV, PSELECT_ELIM, PSELECT_INTRO, PSELECT_RULE.
\ENDDOC