LetExp([
 VarDec(v1,true,NONE,
  IntExp(1)),
 FunctionDec[
  (dummy1,[],
   SOME(int),
   LetExp([
    VarDec(v2,true,NONE,
     IntExp(100)),
    FunctionDec[
     (dummy2,[],
      SOME(int),
      LetExp([
       VarDec(v3,true,NONE,
        IntExp(3)),
       FunctionDec[
        (dummy3,[],
         SOME(int),
         LetExp([
          VarDec(v4,true,NONE,
           IntExp(4)),
          FunctionDec[
           (dummy4,[],
            SOME(int),
            VarExp(
             SimpleVar(v1)))]],
          OpExp(PlusOp,
           VarExp(
            SimpleVar(v3)),
           CallExp(dummy4,[]))))]],
       OpExp(PlusOp,
        VarExp(
         SimpleVar(v2)),
        CallExp(dummy3,[]))))]],
    CallExp(dummy2,[])))]],
 OpExp(PlusOp,
  CallExp(dummy1,[]),
  VarExp(
   SimpleVar(v1))))