c490001.a

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-- C490001.A
--
--                             Grant of Unlimited Rights
--
--     Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,
--     F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained
--     unlimited rights in the software and documentation contained herein.
--     Unlimited rights are defined in DFAR 252.227-7013(a)(19).  By making
--     this public release, the Government intends to confer upon all
--     recipients unlimited rights  equal to those held by the Government.
--     These rights include rights to use, duplicate, release or disclose the
--     released technical data and computer software in whole or in part, in
--     any manner and for any purpose whatsoever, and to have or permit others
--     to do so.
--
--                                    DISCLAIMER
--
--     ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR
--     DISCLOSED ARE AS IS.  THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED
--     WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE
--     SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE
--     OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A
--     PARTICULAR PURPOSE OF SAID MATERIAL.
--*
--
-- OBJECTIVE:
--      Check that, for a real static expression that is not part of a larger
--      static expression, and whose expected type T is a floating point type
--      that is not a descendant of a formal scalar type, the value is rounded
--      to the nearest machine number of T if T'Machine_Rounds is true, and is
--      truncated otherwise. Check that if rounding is performed, and the value
--      is exactly halfway between two machine numbers, one of the two machine
--      numbers is used.
--
-- TEST DESCRIPTION:
--      The test obtains a machine number M1 for a floating point subtype S by
--      passing a real literal to S'Machine. It then obtains an adjacent
--      machine number M2 by using S'Succ (or S'Pred). It then constructs
--      values which lie between these two machine numbers: one (A) which is
--      closer to M1, one (B) which is exactly halfway between M1 and M2, and
--      one (C) which is closer to M2. This is done for both positive and
--      negative machine numbers.
--
--      Let M1 be closer to zero than M2. Then if S'Machine_Rounds is true,
--      C must be rounded to M2, A must be rounded to M1, and B must be rounded
--      to either M1 or M2. If S'Machine_Rounds is false, all the values must
--      be truncated to M1.
--
--      A, B, and C are constructed using the following static expressions:
--
--         A: constant S := M1 + (M2 - M1)*Z; -- Z slightly less than 0.5.
--         B: constant S := M1 + (M2 - M1)*Z; -- Z equals 0.5.
--         C: constant S := M1 + (M2 - M1)*Z; -- Z slightly more than 0.5.
--
--      Since these are static expressions, they must be evaluated exactly,
--      and no rounding may occur until the final result is calculated.
--
--      The checks for equality between the members of (A, B, C) and (M1, M2)
--      are performed at run-time within the body of a subprogram.
--
--      The test performs additional checks that the rounding performed on
--      real literals is consistent for a floating point subtype. A literal is
--      assigned to a constant of a floating point subtype S. The same literal
--      is then passed to a subprogram, along with the constant, and an
--      equality check is performed within the body of the subprogram.
--
--
-- CHANGE HISTORY:
--      25 Sep 95   SAIC    Initial prerelease version.
--      25 May 01   RLB     Repaired to work with the repeal of the round away
--                          rule by AI-268.
--
--!

with System;
package C490001_0 is

   type My_Flt is digits System.Max_Digits;

   procedure Float_Subtest (A, B: in My_Flt; Msg: in String);

   procedure Float_Subtest (A, B, C: in My_Flt; Msg: in String);


--
-- Positive cases:
--

   --  |----|-------------|-----------------|-------------------|-----------|
   --  |    |             |                 |                   |           |
   --  0   P_M1  Less_Pos_Than_Half  Pos_Exactly_Half  More_Pos_Than_Half  P_M2


   Positive_Float : constant My_Flt := 12.440193950021943;

   -- The literal value 12.440193950021943 is rounded up or down to the
   -- nearest machine number of My_Flt when Positive_Float is initialized.
   -- The value of Positive_Float should therefore be a machine number, and
   -- the use of 'Machine in the initialization of P_M1 will be redundant for
   -- a correct implementation. It's done anyway to make certain that P_M1 is
   -- a machine number, independent of whether an implementation correctly
   -- performs rounding.

   P_M1 : constant My_Flt := My_Flt'Machine(Positive_Float);
   P_M2 : constant My_Flt := My_Flt'Succ(P_M1);

   -- P_M1 and P_M2 are adjacent machine numbers. Note that because it is not
   -- certain whether 12.440193950021943 is a machine number, nor whether
   -- 'Machine rounds it up or down, 12.440193950021943 may not lie between
   -- P_M1 and P_M2. The test does not depend on this information, however;
   -- the literal is only used as a "seed" to obtain the machine numbers.


   -- The following entities are used to verify that rounding is performed
   -- according to the value of 'Machine_Rounds. If language rules are
   -- obeyed, the intermediate expressions in the following static
   -- initialization expressions will not be rounded; all calculations will
   -- be performed exactly. The final result, however, will be rounded to
   -- a machine number (either P_M1 or P_M2, depending on the value of
   -- My_Flt'Machine_Rounds). Thus, the value of each constant below will
   -- equal that of P_M1 or P_M2.

   Less_Pos_Than_Half : constant My_Flt := P_M1 + ((P_M2 - P_M1)*2.9/6.0);
   Pos_Exactly_Half   : constant My_Flt := P_M1 + ((P_M2 - P_M1)/2.0);
   More_Pos_Than_Half : constant My_Flt := P_M1 + ((P_M2 - P_M1)*4.6/9.0);


--
-- Negative cases:
--

   --  -|-------------|-----------------|-------------------|-----------|----|
   --   |             |                 |                   |           |    |
   --  N_M2  More_Neg_Than_Half  Neg_Exactly_Half  Less_Neg_Than_Half  N_M1  0


   -- The descriptions for the positive cases above apply to the negative
   -- cases below as well. Note that, for N_M2, 'Pred is used rather than
   -- 'Succ. Thus, N_M2 is further from 0.0 (i.e. more negative) than N_M1.

   Negative_Float : constant My_Flt := -0.692074550952117;


   N_M1 : constant My_Flt := My_Flt'Machine(Negative_Float);
   N_M2 : constant My_Flt := My_Flt'Pred(N_M1);

   More_Neg_Than_Half : constant My_Flt := N_M1 + ((N_M2 - N_M1)*4.1/8.0);
   Neg_Exactly_Half   : constant My_Flt := N_M1 + ((N_M2 - N_M1)/2.0);
   Less_Neg_Than_Half : constant My_Flt := N_M1 + ((N_M2 - N_M1)*2.4/5.0);

end C490001_0;


     --==================================================================--


with TCTouch;
package body C490001_0 is

   procedure Float_Subtest (A, B: in My_Flt; Msg: in String) is
   begin
       TCTouch.Assert (A = B, Msg);
   end Float_Subtest;

   procedure Float_Subtest (A, B, C: in My_Flt; Msg: in String) is
   begin
       TCTouch.Assert (A = B or A = C, Msg);
   end Float_Subtest;

end C490001_0;


     --==================================================================--


with C490001_0;  -- Floating point support.
use  C490001_0;

with Report;
procedure C490001 is
begin
   Report.Test ("C490001", "Rounding of real static expressions: " &
                "floating point subtypes");


   -- Check that rounding direction is consistent for literals:

   Float_Subtest (12.440193950021943, P_M1, "Positive Float: literal");
   Float_Subtest (-0.692074550952117, N_M1, "Negative Float: literal");


   -- Now check that rounding is performed correctly for values between
   -- machine numbers, according to the value of 'Machine_Rounds:

   if My_Flt'Machine_Rounds then
      Float_Subtest (Pos_Exactly_Half,   P_M1, P_M2, "Positive Float: = half");
      Float_Subtest (More_Pos_Than_Half, P_M2, "Positive Float: > half");
      Float_Subtest (Less_Pos_Than_Half, P_M1, "Positive Float: < half");

      Float_Subtest (Neg_Exactly_Half,   N_M1, N_M2, "Negative Float: = half");
      Float_Subtest (More_Neg_Than_Half, N_M2, "Negative Float: > half");
      Float_Subtest (Less_Neg_Than_Half, N_M1, "Negative Float: < half");
   else
      Float_Subtest (Pos_Exactly_Half,   P_M1, "Positive Float: = half");
      Float_Subtest (More_Pos_Than_Half, P_M1, "Positive Float: > half");
      Float_Subtest (Less_Pos_Than_Half, P_M1, "Positive Float: < half");

      Float_Subtest (Neg_Exactly_Half,   N_M1, "Negative Float: = half");
      Float_Subtest (More_Neg_Than_Half, N_M1, "Negative Float: > half");
      Float_Subtest (Less_Neg_Than_Half, N_M1, "Negative Float: < half");
   end if;


   Report.Result;
end C490001;