pred_setLib.SET_SPEC

STRUCTURE

SYNOPSIS

Axiom-scheme of specification for set abstractions.

LIBRARY

pred_set

DESCRIPTION

The conversion SET_SPEC_CONV expects its term argument to be an assertion of the form t IN {E | P}. Given such a term, the conversion returns a theorem that defines the condition under which this membership assertion holds. When E is just a variable v, the conversion returns:

   |- t IN {v | P} = P[t/v]

and when E is not a variable but some other expression, the theorem returned is:

   |- t IN {E | P} = ?x1...xn. (t = E) /\ P

where x1, ..., xn are the variables that occur free both in the expression E and in the proposition P.

EXAMPLE

- SET_SPEC_CONV ``12 IN {n | n > N}``;
|- 12 IN {n | n > N} = 12 > N

- SET_SPEC_CONV ``p IN {(n,m) | n < m}``;
|- p IN {(n,m) | n < m} = (?n m. (p = n,m) /\ n < m)

FAILURE

Fails if applied to a term that is not of the form t IN {E | P}.