:: deftheorem Def19 defines feasible FUNCTOR0:def 19 :
for C1, C2 being non empty AltGraph
for F being Contravariant FunctorStr over C1,C2 holds
( F is feasible iff for o1, o2 being Object of C1 st <^o1,o2^> <> {} holds
<^(F . o2),(F . o1)^> <> {} );