theorem
  for Y being complex-functions-membered set, f being PartFunc of X,Y holds
  f[-]c = f<->(dom f-->c)
  proof
    let Y be complex-functions-membered set, f be PartFunc of X,Y;
    set g = dom f-->c;
A1: dom (f[-]c) = dom f by VALUED_2:def 37;
A2: dom (f<->g) = dom f /\ dom g by VALUED_2:61;
    now
      let x be object;
      assume
A4:   x in dom (f[-]c);
      hence (f[-]c).x = f.x-c by VALUED_2:def 37
      .= f.x-g.x by A1,A4,FUNCOP_1:7
      .= (f<->g).x by A1,A2,A4,VALUED_2:62;
    end;
    hence thesis by A1,A2;
  end;
