reserve X,Y,Z,X1,X2,Y1,Y2 for set, x,y,z,t,x1,x2 for object,
  f,g,h,f1,f2,g1,g2 for Function;

theorem
  dom f1 c= [:X,Y:] & dom f2 c= [:X,Y:] & curry f1 = curry f2 implies f1 = f2
proof
  assume that
A1: dom f1 c= [:X,Y:] and
A2: dom f2 c= [:X,Y:];
  uncurry curry f1 = f1 by A1,Th43;
  hence thesis by A2,Th43;
end;
