
theorem ReplaceValue3:
  for f be FinSequence,
      i,j be Nat,
      a,b being object st
    i in dom f & j in dom f & i <> j holds
    (Replace (f,i,j,a,b)).i = a
  proof
    let f be FinSequence,
        i,j be Nat,
        a,b be object;
    set g = Replace (f,i,j,a,b);
    assume
A1: i in dom f & j in dom f & i <> j; then
    g.i = (f +* (i,a)).i by FUNCT_7:32
       .= a by A1,FUNCT_7:31;
    hence thesis;
  end;
