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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Your wish list for Ada 202X
Date: Sun, 30 Mar 2014 21:33:21 +0200
Organization: cbb software GmbH
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Date: 2014-03-30T21:33:21+02:00
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On Sun, 30 Mar 2014 21:02:00 +0200, Pascal Obry wrote:

> Le dimanche 30 mars 2014 à 05:28 -0700, francois_fabien@hotmail.com a
> écrit : 
>> One wish to ease Input/output :
>> To have some equivalent of C primitive : printf("%c %c %c %c %c \n %c %c %c %c %c \n",
> 
> Well, this is possible in Ada with some coding of a package, one could
> write something like (maybe already implemented by someone, I remember a
> simple_io package or something like that):
> 
>    Formatted_Print 
>       ("%c %c %c %c %c \n %c %c %c %c %c \n"
>        & Var1 & Var2 & Var3 & Var4 & Var5 & Var6 & Var7 & Var8);
> 
> You just have to code the Formatted_Print routine once for all. No big
> deal:
> 
>    type Formatted_String is private;
> 
>    Format_Error : exception;
> 
>    function "&" 
>       (F : Formatted_String; V : Character) return Formatted_String;
>    function "&" 
>       (F : Formatted_String; V : Integer) return Formatted_String;
>    function "&" 
>       (F : Formatted_String; V : Float) return Formatted_String;
>    ...
> 
>    procedure Formatted_Print (F : Formatted_String);
> 
>    procedure Formatted_Print 
>       (File : Text_IO.File_Type; 
>        F    : Formatted_String);

I did such things, it is not so simple.

You need a set of "seed" functions to produce initial Formatted_String,
e.g.

   function "&" (L, R : Character) return Formatted_String;
   function "&" (L : Character; R : Integer) return Formatted_String;
   ...

Or you have to use Empty_Formatted_String constant in each expression.

Another consideration is efficiency, as it would keep on copying the string
upon each concatenation.

One method to deal with that is to use reference counting in
Formatted_String. When the argument F has the reference count 1 it is
updated in place and the result is returned. Otherwise F is cloned, the
copy is updated and then returned.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de