transformation LambdaBool2LambdaNum: LambdaBool ==> LambdaNum {
  transform Exp;

  Exp[true]()                                      ==>  << \x.\y.x >>
     [false]()                                     ==>  << \x.\y.y >>
     [if](E1,E2,E3)  E1()=>X1, E2()=>X2, E3()=>X3  ==>  << ( ( <X1> <X2> ) <X3> ) >>
}