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Date: Tue, 19 May 2009 20:51:23 +0200
From: Olivier Scalbert <olivier.scalbert@algosyn.com>
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Subject: Conversion from floating point to signed 16 bits 
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Date: 2009-05-19T20:51:23+02:00
List-Id: <comp.lang.ada>

Hello,

My problem:
I need to convert an "analogic" value which can vary from 0.0 to 1.0 
into a "discrete" value which is a signed 16 bits integer.

My implementation:
-----------------------------
with Ada.Text_IO;

procedure convert is
     type Analog_Value is digits 10 range 0.0 .. 1.0;
     type Signed_16    is range -32768 .. 32767;
     type Unsigned_16  is range      0 .. 65535;

     function Cv(Value: Analog_Value) return Signed_16 is
         U16: Unsigned_16;
     begin
         U16 := Unsigned_16(65535.0 * Value);
         return Signed_16(U16 - 32768);
     end Cv;

     procedure Put(S16: Signed_16) is
     begin
         Ada.Text_IO.Put_Line(Signed_16'image(S16));
     end put;
begin
    Put(Cv(0.00)); -- Must be -32768
    Put(Cv(0.25)); -- Must be -16384
    Put(Cv(0.50)); -- Must be      0
    Put(Cv(0.75)); -- Must be  16383
    Put(Cv(1.00)); -- Must be  32767
end convert;
-----------------------------

My question:
Is there an other way to do this in Ada (Representation ? Other parts of 
Ada I do not know ?)

My thanks:
Thank you very much !
;-)

Olivier.