\DOC PSELECT_INTRO
\TYPE {PSELECT_INTRO : (thm -> thm)}
\KEYWORDS
rule, epsilon.
\LIBRARY pair
\SYNOPSIS
Introduces an epsilon term.
\DESCRIBE
{PSELECT_INTRO} takes a theorem with an applicative conclusion, say
{P x}, and returns a theorem with the epsilon term {$@ P} in place
of the original operand {x}.
{
A |- P x
-------------- PSELECT_INTRO
A |- P($@ P)
}
The returned theorem asserts that {$@ P} denotes some value
at which {P} holds.
\FAILURE
Fails if the conclusion of the theorem is not an application.
\COMMENTS
This function is exactly the same as {SELECT_INTRO}, it is duplicated in
the pair library for completeness.
\SEEALSO
SELECT_INTRO, PEXISTS, SELECT_AX, PSELECT_CONV, PSELECT_ELIM,
PSELECT_RULE.
\ENDDOC