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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Avoiding side effects
Date: Tue, 30 Sep 2008 03:42:42 -0700 (PDT)
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Date: 2008-09-30T03:42:42-07:00
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Anders Wirzenius wrote:
> I create two functions, Strip and Advance.
> function Strip (Remove_This : in String) return String
>    -- Displays rows until row > Remove_This.
> function Advance (Candidate : in String) return String
>    --  Advance in file until row > Candidate.
> The main program is then merely a loop where I alternate between
> advancing lines in the two files until the row in the file is
> greater than the value to compare against:
...
> The problem is how to deal with the situation when I reach the
> end of the file.
...

Both of your functions already have the side effect of moving the
current position in the input files, so I don't see why you would want
to avoid side effects. I think Jean-Pierre's answer is good; use the
exceptions that Ada.Text_IO propagates to indicate the end of file.

--
Ludovic Brenta.