:: deftheorem Def9 defines MemberFunc ROUGHS_1:def 9 :
for A being finite Tolerance_Space
for X being Subset of A
for b₃ being Function of the carrier of A,REAL holds
( b₃ = MemberFunc (X,A) iff for x being Element of A holds b₃ . x = (card (X /\ (Class ( the InternalRel of A,x)))) / (card (Class ( the InternalRel of A,x))) );