anchor.diff:  
   parses_a_string_containing_a_complex_number_test_() ->
       lists:map(fun({Input,Expected}) ->
  -                      assertComplexWithin(Expected, 0.000000001,  execute(Input, []))
  +                      assertWithin(9, Expected, execute(Input, []))
                 end,
                 [ {"5,3", {5,3}},
                   {"-2.0e-3,5", {-0.002,5}},
  
positive.code: raises_a_number_to_a_power_test_() ->
      [
       ?_assertEqual([32.0], execute ("2 5 **",[])),
       assertComplexWithin({-7.461496614688569,2.8854927255134477}, 0.00000001, execute("2 3,4 **",[])),
       assertComplexWithin({-37.999999999999986,41.000000000000014}, 0.00000001, execute("3,4 2.5 **",[])),
       assertComplexWithin({-14.405859669065997,101.33689785344499}, 0.00000001, execute("1,2 3,-2 **",[]))
      ].
  
  changes_the_sign_of_the_top_number_test_() ->
  
negative.code:     ?assertEqual([0.25], execute("4 \\",[])).
  
  calculates_e_to_the_x_test() ->
      assertWithin(9, 22026.465794807, execute("10 exp",[])).
  
  calculates_the_natural_log_of_x_test() ->
      assertWithin(9, 4.59511985014, execute("99 log",[])).
  
  calculates_the_log_base_10_of_x_test() ->
      assertWithin(9, 1.9956351946, execute("99 log10",[])).
  
  calculates_the_log_base_2_of_x_test() ->
      assertWithin(9, 6.62935662008, execute("99 log2",[])).
  
  % Stack Manipulation
  copies_the_top_value_on_the_stack_test() ->
  