:: deftheorem defines chordal CHORD:def 10 :
for G being _Graph
for W being Walk of G holds
( W is chordal iff ex m, n being odd Nat st
( m + 2 < n & n <= len W & W . m <> W . n & ex e being object st e Joins W . m,W . n,G & ( for f being object st f in W .edges() holds
not f Joins W . m,W . n,G ) ) );