reserve x,y,z for object,
  i,j,n,m for Nat,
  D for non empty set,
  s,t for FinSequence,
  a,a1,a2,b1,b2,d for Element of D,
  p, p1,p2,q,r for FinSequence of D;
reserve M,M1,M2 for Matrix of D;

theorem
  for M being Matrix of 0,m,D holds len M = 0 & width M = 0 & Indices M = {}
proof
  let M be Matrix of 0,m,D;
  len M = 0 by Def2;
  then width M = 0 by Def3;
  then Seg width M = 0;
  hence thesis by Def2,ZFMISC_1:90;
end;
