Converting Binary to Decimal

Converting Binary to Decimal

[WM]

I am writing a program like this:
-----------------------------------------------------------------------
with Ada.Text_Io,Ada.Integer_Text_Io;
use Ada.Text_Io,Ada.Integer_Text_Io;

procedure Bin_2_Dec_Test is

   answer : integer;
   subtype Binary_Number is Integer range 0..1; --define data type
   type a_bin_num is array(1..8) of Binary_Number; --define array type

   bin : Binary_Number;

   function Bin_To_Dec(bin:Binary_Number) return Integer is
      Answer : Integer :=0;
   begin
      for J in reverse 1..8 loop
         Answer := Answer + a_bin_num(Bin(J))*(2**(J-1));
      end loop;
      return Answer;
   end Bin_To_Dec;

begin
   Put_Line("input binary number please: ");
   for num in 1..8 loop
      Get(a_bin_num(num));
   end loop;
   Put_Line("decimal is: ");
   Put(Answer(a_bin_num));
end Bin_2_Dec_Test;
-------------------------------------------------------------------
It gives me a lot of errors... really don't know what's wrong...
Please give some hints, thanks!

RE: Converting Binary to Decimal

[Wilhelm Spickermann]

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On 25-Mar-01 WM wrote:
> I am writing a program like this:
...
>    subtype Binary_Number is Integer range 0..1; --define data type
...
>    function Bin_To_Dec(bin:Binary_Number) return Integer is
...
>          Answer := Answer + a_bin_num(Bin(J))*(2**(J-1));
...
> It gives me a lot of errors... really don't know what's wrong...
> Please give some hints, thanks!

The first error message I get points to Line 16, Character 39 and says:
"array type required in indexed component". The "indexed component" is
"Bin(J)". "Bin" is not an array, it�s an integer (0 or 1). 

The poor naming is the reason of the problems: Rename every occurrence
of "Binary_Number" to "Binary_Digit_Type" and every occurrence of
A_Bin_Num to "Binary_Number_Type" and then look at the function
declaration: Did You really want what is written there?

Wilhelm

Re: Converting Binary to Decimal

[Des Walker]

Hi,

this is not really an answer to your question, please disregard if it is
not relevant.

Have you considered reading your binary number as a string and using
predefined attributes to convert it. e.g.

with Ada.Text_Io; use Ada.Text_Io;

procedure Convert_Test is
  Value_Str : String(1 .. 8);
  Last : Natural;
  Value_Int : Integer;
begin
  Put_Line("input binary number please: ");
  Get_Line(Value_Str, Last);
  Value_Int := Integer'Value("2#" & Value_Str(1 .. Last) & '#');
  Put_Line("Decimal is" & Integer'Image(Value_Int));
end Convert_Test;

Admittedly if the user typed a bad digit, this version would produce a
Constraint Error on the conversion, whereas yours would produce an error
on the Get call.

	Des Walker
	Alenia-Marconi Systems

Re: Converting Binary to Decimal

[Phaedrus]

Simplify, simplify!  If you're going to put together a piece of code
and you're a beginner in the language, try stepping into the problem.

First step, get the input.  Test to make sure you're getting it correctly.
Use meaningful names, please!  For instance, "a_bin_num" implies
that it's a variable, which it isn't.  It's a type, so try calling it
"a_bin_num_type",
that should help to eliminate some confusion.  Also, your "Binary_Number"
(This might be a good time to think about an uppercase/lowercase convention.)
isn't a binary number, it's a binary digit.  Be precise, it pays off when you
start writing longer pieces of code.

Second step, conversion.  If you've got good data in your array, converting
it to the output type should be a piece of cake.

Third (and final) step, output.  Ada makes this easy, but still it's useful
to keep the step alive.  For instance, if you had accidentally set the following
Ada.Integer_Text_Io.Default_Base := 2;
somewhere in your code, you'd realize that everything else was correct and
so the error HAD to be in the output format.  (And no, you can't just set the
Default_Base to 2, and use it to read the number for you.  Shame, isn't it?)

Following the old Input-Process-Output style will get you through a LOT of
programming courses.

Phaedrus

"WM" <wwminirl@hotmail.com> wrote in message
news:99lofd$19j37@tech.port.ac.uk...
> I am writing a program like this:
> -----------------------------------------------------------------------
> with Ada.Text_Io,Ada.Integer_Text_Io;
> use Ada.Text_Io,Ada.Integer_Text_Io;
>
> procedure Bin_2_Dec_Test is
>
>    answer : integer;
>    subtype Binary_Number is Integer range 0..1; --define data type
>    type a_bin_num is array(1..8) of Binary_Number; --define array type
>
>    bin : Binary_Number;
>
>    function Bin_To_Dec(bin:Binary_Number) return Integer is
>       Answer : Integer :=0;
>    begin
>       for J in reverse 1..8 loop
>          Answer := Answer + a_bin_num(Bin(J))*(2**(J-1));
>       end loop;
>       return Answer;
>    end Bin_To_Dec;
>
> begin
>    Put_Line("input binary number please: ");
>    for num in 1..8 loop
>       Get(a_bin_num(num));
>    end loop;
>    Put_Line("decimal is: ");
>    Put(Answer(a_bin_num));
> end Bin_2_Dec_Test;
> -------------------------------------------------------------------
> It gives me a lot of errors... really don't know what's wrong...
> Please give some hints, thanks!
>
>
>

Re: Converting Binary to Decimal - holy war alert

[Martin Dowie]

'a_bin_num' doesn't imply it's a variable - 'a' is the "indefinate article"
and
can be used to indicate the type of something without specifying _which_
item you are talking about e.g.

  My_Kettle : A_Kettle := (Make => Kenwood, Capacity_In_Litres => 1.5, --
etc);
  Your_Kettle : A_Kettle := (Make => Bosch, Capacity_In_Litres => 2.0, --
etc);
etc.


Phaedrus <phaedrusalt@hotmail.com> wrote in message
news:n3Ov6.15480$ue1.1287176@newsread2.prod.itd.earthlink.net...
> First step, get the input.  Test to make sure you're getting it correctly.
> Use meaningful names, please!  For instance, "a_bin_num" implies
> that it's a variable, which it isn't.  It's a type, so try calling it
> "a_bin_num_type",

Re: Converting Binary to Decimal - holy war alert

[Phaedrus]

In that case, would you please deliver to me A_Billion_Dollars?  I don't care
which billion dollars you deliver.

The point I was trying to get across was that unless something is explicitly
shown as a type, it tends to look like a variable.  That's why I use the
convention
"_type" post-pended to my type definitions, and that's what I was recommending
for his use, too.  It's pretty hard to confuse "A_Dog_Type" with an actual
instance
of the type, and try to feed it or something.

So, when do you think you can deliver the money?

Phaedrus
"Martin Dowie" <martin.dowie@baesystems.com> wrote in message
news:3ac19bdf$1@pull.gecm.com...
> 'a_bin_num' doesn't imply it's a variable - 'a' is the "indefinate article"
> and
> can be used to indicate the type of something without specifying _which_
> item you are talking about e.g.
>
>   My_Kettle : A_Kettle := (Make => Kenwood, Capacity_In_Litres => 1.5, --
> etc);
>   Your_Kettle : A_Kettle := (Make => Bosch, Capacity_In_Litres => 2.0, --
> etc);
> etc.
>
>
> Phaedrus <phaedrusalt@hotmail.com> wrote in message
> news:n3Ov6.15480$ue1.1287176@newsread2.prod.itd.earthlink.net...
> > First step, get the input.  Test to make sure you're getting it correctly.
> > Use meaningful names, please!  For instance, "a_bin_num" implies
> > that it's a variable, which it isn't.  It's a type, so try calling it
> > "a_bin_num_type",
>
>
>
>

Re: Converting Binary to Decimal - holy war alert

[Martin Dowie]

On A_Day :-)

Seriously though the 'A_'/'An_' notation is used in some s/w houses (I know
of 3 spread across the UK), precisely to to highlight the difference between
the abstract and the specific.

Phaedrus <phaedrusalt@hotmail.com> wrote in message
news:bhqw6.5005$aP5.412427@newsread2.prod.itd.earthlink.net...
> In that case, would you please deliver to me A_Billion_Dollars?  I don't
care
> which billion dollars you deliver.

Re: Converting Binary to Decimal - holy war alert

[Robert A Duff]

"Martin Dowie" <martin.dowie@baesystems.com> writes:

> Seriously though the 'A_'/'An_' notation is used in some s/w houses (I know
> of 3 spread across the UK), precisely to to highlight the difference between
> the abstract and the specific.

It's used in Smalltalk, too.  Eg, if a method takes two Strings, they
will typically be called aString and anotherString.  You can't declare
that they're of type String in Smalltalk -- the name of the thing (or a
comment) is the only hint.

- Bob