RE: Convert array to integer value

RE: Convert array to integer value

[Beard, Frank [Contractor]]

Assuming you have your 16 bit integer defined something
like the following:

with Ada.Text_Io;
with Ada.Unchecked_Conversion;

procedure BitTest is

   type Word is range -2**15 .. 2**15-1;
   for Word'size use 16;

   type Bit is mod 2;
   for Bit'size use 1;

   type Bit_Array is array (1..16) of Bit;
   pragma Pack(Bit_Array);

   function To_Integer is new
      Ada.Unchecked_Conversion(Source => Bit_Array,
                               Target => Word);

   bits   : Bit_Array := (others => 0);
   result : Word := 0;

   char   : character := ' ';

begin

   --+ Results on Windows.  Your order will
   --+ vary based on the bit order on your machine.
   --+ On Windows: High Order bit is index 16
   --+             Low  Order bit is index 1.
   --+ Running with the first two "bits" values below
   --+ will tell you immediately what you need to know.

   bits := (0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1);  --+ -32768
-- bits := (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0);  --+  1
-- bits := (1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0);  --+  7

   result := To_Integer(bits);

   Ada.Text_Io.New_Line;

   Ada.Text_Io.Put_Line("Word [" & Word'image(result) & " ]");

   Ada.Text_Io.New_Line;

   Ada.Text_Io.Put("Hit any key to continue ...");
   Ada.Text_Io.Get_Immediate(char);

end BitTest;


Frank


-----Original Message-----
From: Stephen Frackelton [mailto:stephen.frackelton@baesystems.com]
Sent: Thursday, May 23, 2002 10:49 AM
To: comp.lang.ada@ada.eu.org
Subject: Convert array to integer value


I have set up an array of integers, value 0..1, to simulate a word, 16 bits.

I need to convert this array of 0's and 1's from the binary value to its
corresponding integer value.

is there any simple way of doing this ?

All i can think of is for loop through the array and having a translation
table for each position within the array, i.e if bit 5 = 1 then add 16 to
total, if bit 6 = 1 then add 32 to total and so on.

any other ideas ?


thanks

Stephen


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Convert array to integer value

[Stephen Frackelton]

I have set up an array of integers, value 0..1, to simulate a word, 16 bits.

I need to convert this array of 0's and 1's from the binary value to its
corresponding integer value.

is there any simple way of doing this ?

All i can think of is for loop through the array and having a translation
table for each position within the array, i.e if bit 5 = 1 then add 16 to
total, if bit 6 = 1 then add 32 to total and so on.

any other ideas ?


thanks

Stephen

Re: Convert array to integer value

[Nige]

Stephen Frackelton wrote:
> 
> I have set up an array of integers, value 0..1, to simulate a word, 16 bits.
> 
> I need to convert this array of 0's and 1's from the binary value to its
> corresponding integer value.
> 
> is there any simple way of doing this ?
> 
> All i can think of is for loop through the array and having a translation
> table for each position within the array, i.e if bit 5 = 1 then add 16 to
> total, if bit 6 = 1 then add 32 to total and so on.
> 
> any other ideas ?

If you make it an array of booleans, you can pack the array into 16
bits, then do an unchecked conversion into an unsigned_16 on the
array...

Also, a boolean array will allow you to do logical operations too...

Nige

Re: Convert array to integer value

[Stephen Frackelton]

thanks, will consider this in future, but this would involve too many
changes now...

any others ?

"Nige" <nigel.scott@uk.thalesgroup.com> wrote in message
news:3CED0420.5C5A9B6D@uk.thalesgroup.com...
> Stephen Frackelton wrote:
> >
> > I have set up an array of integers, value 0..1, to simulate a word, 16
bits.
> >
> > I need to convert this array of 0's and 1's from the binary value to its
> > corresponding integer value.
> >
> > is there any simple way of doing this ?
> >
> > All i can think of is for loop through the array and having a
translation
> > table for each position within the array, i.e if bit 5 = 1 then add 16
to
> > total, if bit 6 = 1 then add 32 to total and so on.
> >
> > any other ideas ?
>
> If you make it an array of booleans, you can pack the array into 16
> bits, then do an unchecked conversion into an unsigned_16 on the
> array...
>
> Also, a boolean array will allow you to do logical operations too...
>
> Nige

Re: Convert array to integer value

[Stephen Leake]

"Stephen Frackelton" <stephen.frackelton@baesystems.com> writes:

> thanks, will consider this in future, but this would involve too many
> changes now...
> 
> any others ?

You can pack your integer array (make sure they are unsigned
integers), and do unchecked conversion on that as well.


-- 
-- Stephe

Re: Convert array to integer value

[David Gillon]

Stephen Frackelton wrote:
> I have set up an array of integers, value 0..1, to simulate a word, 16 bits.
> I need to convert this array of 0's and 1's from the binary value to its
> corresponding integer value.
> is there any simple way of doing this ?
> All i can think of is for loop through the array and having a translation
> table for each position within the array, i.e if bit 5 = 1 then add 16 to
> total, if bit 6 = 1 then add 32 to total and so on.
> any other ideas ?

Without getting into questions over why you would want to use a
datastructure like that, try the following algorithm:

Sum = 0
For Count = 1 to 16 
  Sum = Sum + ((2 ** Count-1) * Integer_Array(Count))

(And there's also a perfectly good internal company newsgroup for Ada
questions)
 
-- 


David Gillon

Re: Convert array to integer value

[Stuart Palin]

David Gillon wrote:
> 
> Stephen Frackelton wrote:
> > I have set up an array of integers, value 0..1, to simulate a
> > word, 16 bits.  I need to convert this array of 0's and 1's
> > from the binary value to its corresponding integer value.

> Without getting into questions over why you would want to use a
> datastructure like that, try the following algorithm:

Agreed.

The Stephen Leake suggestion is possibly the best if you
have control over the declaration of the array, and the
array is not being used for other purposes which would make
it desirable to access each element as a simple entity
(issues of execution performance may become relevant in that
case).

I think David's suggestion can be tidied a bit; I would
suggest an algorithm such as

  Sum := 0;
  for i in reverse 1..15 loop
    Sum := Sum*2 + My_Array(i);
  end loop;
  if (My_Array(16) = 1) then
    Sum := Sum - 65536;
  end if;

[ If your compiler is too dumb to optimize the *2 to either
a shift or an add then re-write it yourself as Sum+Sum].


> (And there's also a perfectly good internal company newsgroup for Ada
> questions)
Seconded!

--
Stuart Palin
Principal Software Engineer
BAE SYSTEMS Avionics Ltd, Rochester