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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Subject: Re: new_line in a put_line
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Date: 2002-12-02T15:49:29+00:00
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"Vlad" <vbednikov@optusnet.com.au> writes:

> Is there a way of prepending a new_line to a put_line.
> The reason I need this is that I have multiple tasks outputing to a\
> single file. Some of them use Text_IO.Put rather then Text_IO.Put_Line.
> And because of this, some of these outputs get written on the same line
> as my outputs.

You seem to be assuming that each call to Put or Put_Line is atomic.
That's not true, so inserting a new-line into the string passed to
Put_Line is not a correct solution.

If one task says:

    Put_Line("Hello");

and another task simultaneously says:

    Put_Line("Goodbye");

the program is erroneous, which means it can have totally unpredictable
behavior.  It might intersperse the characters, so you get:

    HelGoodl
    obye

or it might print what you want:

    Hello
    Goodbye

or it might crash, or anything else.

What you need to do is synchronize your accesses to the standard output
file, perhaps using a protected object.

- Bob