:: deftheorem defines Regular GEOMTRAP:def 15 :
for IT being non empty AffinStruct holds
( IT is Regular iff for p, q, a, a1, b, b1, c, c1, d, d1 being Element of IT st p <> q & p,q // a,a1 & p,q // b,b1 & p,q // c,c1 & p,q // d,d1 & a,b // c,d holds
a1,b1 // c1,d1 );