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From: stefan-lucks@see-the.signature
Newsgroups: comp.lang.ada
Subject: Re: Disabling string evaluation in a logging system
Date: Tue, 18 May 2010 12:13:01 +0200
Organization: Bauhaus-Universitaet Weimar
Message-ID: <Pine.LNX.4.64.1005181148170.19671@medsec1.medien.uni-weimar.de>
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Date: 2010-05-18T12:13:01+02:00
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On Tue, 18 May 2010, dhenry wrote:

[...]
> Log.Write ("Parameter " & To_String (Param_Name) & " Value = " &
> Integer'Image (X), Log_Level);
> 
> If the Log_Level variable is set to 0 (logging disabled), the
> application will still evaluate the Text parameter, before testing the
> Level parameter to know if we finally must write it into the file or
> not.
[...]
> if Log_Level > 0 then
>   Log.Write ("Parameter " & To_String (Param_Name) & " Value = " &
> Integer'Image (X), Log_Level);
> end if;
> 
> But with thousands of logging lines everywhere in my application, it
> will make the code quite unreadable and introduces a lot of if-test
> pollution (and it's really boring to write).

How about the following?

package Log is 

  type Level_Type is range 0 .. 5;

  procedure Write(Message: String; 
                  Log_Level: Level_Type);

  -- The above is, what you have, so far. 
  -- The stuff below is new:

  procedure Write(Message_1: String; 
                  Message_2: String;
                  Log_Level: Level_Type);
  -- if Log_Level>0 then 
  --    Write(Message_1 & Message_2, Log_Level); 
  -- end if

  procedure Write(Message_1: String; 
                  Message_2: String;
                  Message_3: String
                  Log_Level: Level_Type);
  -- if Log_Level>0 then ... 

  ...

end Log;

If you are willing to change the order of your parameters, one flexible 
Write-procedure would suffice:

with Log;

package Flexi_Log is

  procedure Write(Log_Level: Log.Level_Type;
                  Message_1: String := "";
                  Message_2: String := "";
                  Message_3: String := "";
                  ...
                  Message_9: String := "");
  -- if Log_Level>0 then
  --   Log.Write(Message_1 & Message_2 & ... , Log_Level);
  -- end if;

end Flexi_Log;

In any case, the number of different strings to make one message is 
constant. The constant is under your control, but it is constant. If your 
support goes for up to, say, Message_9, a message for the log which 
consists of 10 or more parts may still trouble you. So change the constant 
sufficiently large that it doesn't trouble you too often ...

I hope that helps!

Stefan


-- 
------ Stefan Lucks   --  Bauhaus-University Weimar  --   Germany  ------
               Stefan dot Lucks at uni minus weimar dot de
------  I  love  the  taste  of  Cryptanalysis  in  the  morning!  ------