Re: Avoiding side effects

[Anders Wirzenius <anders@no.email.thanks.invalid>]

Ludovic Brenta <ludovic@ludovic-brenta.org> writes:

> 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.

Yes, you are right. 
The design in itself contains at least one side effect.
Thanks to both of you, Jean-Pierre and Ludovic.

-- 
Anders