Stephen,
Very clever. Thank you.
Richard Riehle
============================================================
"Stephen Leake" <Stephe.Leake@[EMAIL PROTECTED]
> wrote in message
news:umymuph04.fsf@[EMAIL PROTECTED]
> <adaworks@[EMAIL PROTECTED]
> writes:
>
>> I am looking for some short, practical examples of the Epsilon
>> attribute. If you do have some source code examples to post,
>> please also send them to my academic email: rdriehle@[EMAIL PROTECTED]
>
> -- These values guarantee Integer_16 (value) or Unsigned_16
> -- (value) won't raise Constraint_Error, and allow for maximum
> -- round-off error. Useful with Clip_Scale_Limit when result will
> -- be converted to Integer_16 or Unsigned_16.
> Integer_16_First_Real : constant Real_Type := Real_Type
> (Interfaces.Integer_16'First) - 0.5 +
> (Real_Type'Epsilon * Real_Type (Interfaces.Integer_16'Last));
>
> Integer_16_Last_Real : constant Real_Type := Real_Type
> (Interfaces.Integer_16'Last) + 0.5 -
> (Real_Type'Epsilon * Real_Type (Interfaces.Integer_16'Last));
>
> Unsigned_16_First_Real : constant Real_Type := -0.5 +
Real_Type'Epsilon;
> Unsigned_16_Last_Real : constant Real_Type := Real_Type
> (Interfaces.Unsigned_16'Last) + 0.5 -
> (Real_Type'Epsilon * Real_Type (Interfaces.Unsigned_16'Last));
>
>
> function First_Order_Trig return Real_Type
> is begin
> return Elementary.Sqrt (Real_Type'Model_Epsilon);
> end First_Order_Trig;
>
> function Half_Trig (Trig : in Trig_Pair_Type) return Trig_Pair_Type
> is
> -- The result Trig.Cos is >= 0.0.
> --
> -- A linear approximation is used when Trig.Sin <
> -- First_Order_Trig. this is exact since cos x = 1 - x**2 for
> -- this range of x.
> begin
> if abs Trig.Sin < First_Order_Trig then
> -- angle near 0 or Pi.
> if Trig.Cos > 0.0 then
> -- angle near 0
> return (Trig.Sin / 2.0, 1.0);
> else -- angle near Pi
> if Trig.Sin >= 0.0 then
> return (1.0 - Trig.Sin / 2.0, 0.0);
> else
> return (-1.0 + Trig.Sin / 2.0, 0.0);
> end if;
> end if;
> else -- angle not near 0 or Pi
> if Trig.Sin >= 0.0 then
> return (Elementary.Sqrt ((1.0 - Trig.Cos) / 2.0),
Elementary.Sqrt
> ((1.0 + Trig.Cos) / 2.0));
> else
> return (-Elementary.Sqrt ((1.0 - Trig.Cos) / 2.0),
Elementary.Sqrt
> ((1.0 + Trig.Cos) / 2.0));
> end if;
> end if;
> end Half_Trig;
>
> --
> -- Stephe
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