dflog_nobserver_impl
====================

A nobserver that has an associated dataframe, to which logging information about
patterns and macro variables is written on the trigger event.

description
-----------

	some_dflog description

The description of `some_dflog` will contain an element `Patterns` that lists
the patterns that are written to the dataframe on trigger events.

default_dataframe
-----------------

	some_dflog default_dataframe

Return the dataframe that is managed by `some_dflog`.

get_dataframe
-------------

	some_dflog get_dataframe

Return that dataframe that is currently used by `some_dflog`.  On creation, this is
the same as `(some_dflog default_dataframe)`.

set_dataframe
-------------

	some_dflog set_dataframe some_df

Redirect the logging of `some_dflog` to `some_df`.

add_variable
------------

	some_dflog add_variable macname

Add the macro variable called `macname` (without the $) to the list of information
logged when a trigger event occurs.

add_pattern
-----------

	some_dflog add_pattern pat

Add the pattern `pat` to the list of information logged when a trigger event occurs.