NAME
    DelayLine - Simple time-delay data stucture

SYNOPSIS
        use DelayLine;

        my $dl = DelayLine->new(delay => $defaultdelay);

        $dl->in($item);

        [ ... ]

        if (my $ob = $dl->out()) {
            # do stuff with $ob
        }

DESCRIPTION
    The `DelayLine' is a simple two-port data structure, like a FIFO, but
    with variable delay. Each object put into the input of the DelayLine
    will appear on the output only after some pre-determined amount of time
    has elapsed. This time can be set as a default for the DelayLine, or can
    be individually overridden for each object put into the DelayLine.

    If the default delay time is set to zero, and is not overridden for the
    individual objects, the DelayLine mimics a straightforward FIFO.

    The DelayLine accepts any scalar value as input, including references.

    The DelayLine is a very useful component when building simple event
    loops.

  Methods

    `DelayLine' provides the following methods:

    DelayLine->new( [ delay => DELAY [, debug => DEBUG ]] )
        Returns a newly created `DelayLine' object.

        The default delay is 0 seconds, unless an optional `DELAY' time in
        seconds is given.

        Debugging is turned off by default. Setting DEBUG to true, enables
        debugging output to STDOUT.

        The parameter naming style is very flexible: the keyword can be in
        lower, upper or mixed case, and can be optionally prefixed with a
        dash. Thus, the following are all equivalent:

          $dl = DelayLine->new( -delay => 42 );
          $dl = DelayLine->new(  delay => 42 );
          $dl = DelayLine->new( -Delay => 42 );
          $dl = DelayLine->new(  DELAY => 42 );
          $dl = DelayLine->new( -deLaY => 42 );

        `new()' can be called as a class (static) or object method. Calling
        `new()' as an object method is only a convenience; no data from the
        original DelayLine is carried over into the newly created object.

    $DL->in( OBJ [, DELAY ] )
        This method puts object `OBJ' into DelayLine `$DL'.

        The object `OBJ' can be any scalar value, including references.

        The default delay as set in the `new()' method is used, unless
        overridden by setting `DELAY'.

    $DL->out()
        This method fetches objects from the out from the DelayLine `$DL'.

        Returns the first of the timed-out objects, if any.

        Returns `undef' if the DelayLine is empty, of if no objects in the
        DelayLine have timed out yet.

    $DL->delay( [ DELAY ] )
        Returns the current default delay setting of the DelayLine. If the
        optional value DELAY is set, sets a new default delay value.

    $DL->debug( [ DEBUG ] )
        Returns the current debug setting of the DelayLine. If the optional
        value DEBUG is set, sets a new debug value.

        If the debug value is set (true), calling any of the 'active'
        methods (`in()' or `out()' will yield a short debug message on
        STDERR.

BUGS
    This is a fairly simple module, so no serious bugs are expected. Patches
    are welcome, though.

RELEASE HISTORY
    v0.02 - 2000-jul-22
    Fixed test for multiple unknown args. Removed superfluous test output.
    Streamlined debug output.

    v0.01 - 2000-jul-13
    Initial release.

COPYRIGHT
    Copyright (c) 2000 Lars Thegler. All rights reserved.

    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

AUTHOR
    Lars Thegler <lars@thegler.dk>