reserve a,b,c,d,x,y,w,z,x1,x2,x3,x4 , X for set;
reserve A for non empty set;
reserve i,j,k for Element of NAT;
reserve a,b,c,d for Real;
reserve y,r,s,x,t,w for Element of RAT+;

theorem Th15:
  for f being Function of 4,REAL ex a,b,c,d st f = (0,1,2,3)-->(a,b,c,d)
proof
  let f be Function of 4,REAL;
  reconsider a = f.0, b = f.1, c = f.2, d = f.3 as Element of REAL
       by XREAL_0:def 1;
  take a,b,c,d;
  dom f = {0,1,2,3} by CARD_1:52,FUNCT_2:def 1;
  hence thesis by FUNCT_4:144;
end;
