Instance CompSpecs : compspecs.Definition Vprog : varspecs.Definition Gprog: funspecs := nil.Definition Delta1 : tycontext :=
  ltac:(let x := constr:(func_tycontext f_sumarray Vprog Gprog nil)
         in let y := eval hnf in x
         in exact y).

Lemma exercise2: forall x, Int.min_signed <= x <= Int.max_signed -> Int.signed (Int.repr x) = x.