def optimize_tail_calls(original_scheme_eval): """Return a properly tail recursive version of an eval function.""" def optimized_eval(expr, env, tail=False): """Evaluate Scheme expression EXPR in Frame ENV. If TAIL, return an Unevaluated containing an expression for further evaluation. """ if tail and not scheme_symbolp(expr) and not self_evaluating(expr): return Unevaluated(expr, env) result = Unevaluated(expr, env) # fill in code code here while isinstance(result, Unevaluated): #code here return optimized_eval scheme_eval = optimize_tail_calls(scheme_eval)

the code is in ada   with Ada.Numerics.Generic_Elementary_Functions; package body Number_Theory is    -- Instantiate the library for floating point math using Floating_Type.   package Floating_Functions is new Ada.Numerics.Generic_Elementary_Functions(Floating_Type);   use Floating_Functions;    function Factorial(N : in Factorial_Argument_Type) return Positive is   begin      -- TODO: Finish me!      --      -- 0! is 1      -- N! is N * (N-1) * (N-2) * ... * 1      return 1;   end Factorial;    function Is_Prime(N : in Prime_Argument_Type) return Boolean is      Upper_Bound     : Prime_Argument_Type;      Current_Divisor : Prime_Argument_Type;   begin      -- Handle 2 as a special case.      if N = 2 then         return True;      end if;       Upper_Bound := N - 1;      Current_Divisor := 2;      while Current_Divisor < Upper_Bound loop         if N rem Current_Divisor = 0 then            return False;         end if;         Upper_Bound := N / Current_Divisor;      end loop;…