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From: Samuel Tardieu <sam@rfc1149.net>
Newsgroups: comp.lang.ada
Subject: Re: and then... (a curiosity)
References: 
 <18b41828-bda4-4484-8884-ad62ce1c831d@f36g2000hsa.googlegroups.com>
Date: Fri, 29 Aug 2008 23:47:25 +0200
Message-ID: <874p53bij6.fsf@willow.rfc1149.net>
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Date: 2008-08-29T23:50:02+02:00
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> I wondered why in Ada the "shortcut and" is "and then", while the
> simple "and" has not a shortcut behaviour.  My curiosity stems from
> the fact that I am not able to envision any situation where the "non
> shortcut" version would preferable, but I immagine that there was
> some reason for this choice.  Do anyone have any hint?

Sometimes, you want to ensure that both sides of the boolean operator
have been evaluated. Here is an example:

  --  Send the message to the log and return True if it
  --  has been logged at least at one place succesfully.

  function Log (Message : String) return Boolean is
  begin
     return Log_To_Network (Message) or Log_To_Disk (Message);
  end Log;

 Sam
-- 
Samuel Tardieu -- sam@rfc1149.net -- http://www.rfc1149.net/