:: deftheorem Def2 defines convex CONVEX1:def 2 :
for V being non empty RLSStruct
for M being Subset of V holds
( M is convex iff for u, v being VECTOR of V
for r being Real st 0 < r & r < 1 & u in M & v in M holds
(r * u) + ((1 - r) * v) in M );