Newbie Q: Zero fill in Put

Newbie Q: Zero fill in Put

[Larry Coon]

I looked through the docs I have & the FAQ
on Ada Home, but I didn't see an answer to
what I hope is a simple question. How does
one zero-fill for integers in a Put call?

eg:

declare
   x: integer := 2;
   package int_io is new integer_io(integer);
   use int_io;
begin
   Put(x);
end;

How do I make it output with leading zeros,
eg: 02, 002, 00000002, etc?  The width parameter
seems to only fill with spaces.

Larry Coon
larry@fs2.assist.uci.edu
and lmcoom@home.com

Re: Newbie Q: Zero fill in Put

[Jacob Sparre Andersen]

Larry Coon (lmcoon@home.com) wrote:
 __________
| I looked through the docs I have & the FAQ
| on Ada Home, but I didn't see an answer to
| what I hope is a simple question. How does
| one zero-fill for integers in a Put call?
 ^^^^^^^^^^
|^^^^^^^^^^
| How do I make it output with leading zeros,
| eg: 02, 002, 00000002, etc?  The width parameter
| seems to only fill with spaces.
|__________

I do not think there is a routine to do it in the standard libraries, but it
is not hard to implement with a few calls to routines in the standard 
libraries.

(warning: untested, uncompiled, and probably incorrect code)

   with Ada.Strings.Fixed;
   with Ada.Text_IO;

   generic

      type Num is range <>;

      Fill : Character := '0';

   procedure Put (File    : in     Ada.Text_IO.File_Type;
                  Item    : in     Num;
                  Fill_To : in     Positive) is

      use Ada.Strings;
      use Ada.Strings.Fixed;
      use Ada.Text_IO;

      Buffer : String (1 .. Fill_To);

   begin --  Put
      Move (Target  => Buffer,
            Source  => Trim (Item'Image, Both),
            Pad     => Fill,
            Justify => Right);
      Put (File => File,
           Item => Buffer);
   end Put;

Greetings,

Jacob
--
Jacob Sparre Andersen                       Web:   http://fys.ku.dk/%7Esparre/
Center for Chaos and Turbulence Studies     Phone: (+45) 39 65 53 51
The Niels Bohr Institute                           (+45) 35 32 53 05
--
Try Ada 95 - The programming language of today - and tomorrow!

Re: Newbie Q: Zero fill in Put

[John Herro]

Larry Coon <lmcoon@home.com> writes:
> How do I make [integers] output with
> leading zeros, eg: 02, 002, 00000002, etc?
> The width parameter seems to only fill with
> spaces.
     Here's one way to do it that works in Ada 83 as well as Ada 95.  Let
J be the integer and W be the width that you want.  I assume the integer is
non-negative and that it will fit in W spaces.  Add J to 10**W (here I
assume that this will not overflow).  Take the Integer'Image of the result,
which will always have a length of W+2 because of the leading space. 
Select the slice (3 .. W+2).
     For example, if J is 2 and you want a width of 3, this will print 002:
Ada.Text_IO.Put(Integer'Image(1000 + J)(3 .. 5));
     Obviously, this works with any integer type.  For example, many
compilers have Long_Integer.
     There are other ways to do what you want, but this way is quick and
simple if you know that J will never be large enough to cause an overflow. 
I hope this helps.
- John Herro
Software Innovations Technology
http://members.aol.com/AdaTutor
ftp://members.aol.com/AdaTutor

Re: Newbie Q: Zero fill in Put

[Pascal Obry]

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Another solution is to use the Ada.Text_IO.Editing package.
This package is able to format decimal number with great simplicity
(the functionalities are derived from the COBOL pictures) and is
very powerfull.

This is maybe a complex solution for a simple problem but in some
others complex cases it is very usefull.

-----------------------------------------

with Ada.Text_IO.Editing;

procedure Zfill is

   use Ada;

   type Num is delta 0.1 digits 10;

   package Text_Editing is new Text_IO.Editing.Decimal_Output (Num);

   X : Integer := 2;

begin
   Text_Editing.Put (Num (X), Pic => Text_IO.Editing.To_Picture ("999"));
end Zfill;

--

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Re: Newbie Q: Zero fill in Put

[Robert Dewar]

<<How do I make it output with leading zeros,
eg: 02, 002, 00000002, etc?  The width parameter
seems to only fill with spaces.>>

If you are using GNAT, which fully implements the information systems
annex, then consider using Ada.Text_IO.Editing with an appropriate
picture string.

Re: Newbie Q: Zero fill in Put

[Robert Dewar]

Jacob says (of outputting numbers with leading zeroes)

<<I do not think there is a routine to do it in the standard libraries, but it
is not hard to implement with a few calls to routines in the standard
libraries.>>


No, that's wrong, there are extensive formatting capabilities defined in
Ada 95 that share the concept of COBOL picture strings. This is a particularly
trivial case (you just use a picture of all 9's). Have a look at the package
Ada.Text_IO.Editing in annex G. This capability is fully implemented in all
current versions of GNAT.

Re: Newbie Q: Zero fill in Put

[Larry Coon]

Thanks to everybody who replied.  I got it
working.

Larry Coon
University of California
larry@fs2.assist.uci.edu
and lmcoom@home.com