let W be Function; :: thesis: for G being finite Graph
for P being oriented Chain of G
for v1, v2 being Element of G st P is_orientedpath_of v1,v2 & W is_weight>=0of G holds
ex q being oriented Simple Chain of G st q is_shortestpath_of v1,v2,W
let G be finite Graph; :: thesis: for P being oriented Chain of G
for v1, v2 being Element of G st P is_orientedpath_of v1,v2 & W is_weight>=0of G holds
ex q being oriented Simple Chain of G st q is_shortestpath_of v1,v2,W
let P be oriented Chain of G; :: thesis: for v1, v2 being Element of G st P is_orientedpath_of v1,v2 & W is_weight>=0of G holds
ex q being oriented Simple Chain of G st q is_shortestpath_of v1,v2,W
let v1, v2 be Element of G; :: thesis: ( P is_orientedpath_of v1,v2 & W is_weight>=0of G implies ex q being oriented Simple Chain of G st q is_shortestpath_of v1,v2,W )
assume that
A1: P is_orientedpath_of v1,v2 and
A2: W is_weight>=0of G ; :: thesis: ex q being oriented Simple Chain of G st q is_shortestpath_of v1,v2,W
AcyclicPaths (v1,v2) <> {} by A1, Th41;
then consider r being FinSequence of the carrier' of G such that
A3: r in AcyclicPaths (v1,v2) and
A4: for s being FinSequence of the carrier' of G st s in AcyclicPaths (v1,v2) holds
cost (r,W) <= cost (s,W) by Th50;
consider t being oriented Simple Chain of G such that
A5: r = t and
A6: t is_acyclicpath_of v1,v2 by A3;
take t ; :: thesis: t is_shortestpath_of v1,v2,W
thus t is_orientedpath_of v1,v2 by A6; :: according to GRAPH_5:def 17 :: thesis: for q being oriented Chain of G st q is_orientedpath_of v1,v2 holds
cost (t,W) <= cost (q,W)