Enable display of debugging messages while doing pattern matching.
        Set ``flag`` to True to enable, False to disable.

        Example::

            wd = Word(alphas).setName("alphaword")
            integer = Word(nums).setName("numword")
            term = wd | integer

            # turn on debugging for wd
            wd.setDebug()

            OneOrMore(term).parseString("abc 123 xyz 890")

        prints::

            Match alphaword at loc 0(1,1)
            Matched alphaword -> ['abc']
            Match alphaword at loc 3(1,4)
            Exception raised:Expected alphaword (at char 4), (line:1, col:5)
            Match alphaword at loc 7(1,8)
            Matched alphaword -> ['xyz']
            Match alphaword at loc 11(1,12)
            Exception raised:Expected alphaword (at char 12), (line:1, col:13)
            Match alphaword at loc 15(1,16)
            Exception raised:Expected alphaword (at char 15), (line:1, col:16)

        The output shown is that produced by the default debug actions - custom debug actions can be
        specified using :class:`setDebugActions`. Prior to attempting
        to match the ``wd`` expression, the debugging message ``"Match <exprname> at loc <n>(<line>,<col>)"``
        is shown. Then if the parse succeeds, a ``"Matched"`` message is shown, or an ``"Exception raised"``
        message is shown. Also note the use of :class:`setName` to assign a human-readable name to the expression,
        which makes debugging and exception messages easier to understand - for instance, the default
        name created for the :class:`Word` expression without calling ``setName`` is ``"W:(ABCD...)"``.

def setDebug( self, flag=True ):
        """
        Enable display of debugging messages while doing pattern matching.
        Set ``flag`` to True to enable, False to disable.

        Example::

            wd = Word(alphas).setName("alphaword")
            integer = Word(nums).setName("numword")
            term = wd | integer

            # turn on debugging for wd
            wd.setDebug()

            OneOrMore(term).parseString("abc 123 xyz 890")

        prints::

            Match alphaword at loc 0(1,1)
            Matched alphaword -> ['abc']
            Match alphaword at loc 3(1,4)
            Exception raised:Expected alphaword (at char 4), (line:1, col:5)
            Match alphaword at loc 7(1,8)
            Matched alphaword -> ['xyz']
            Match alphaword at loc 11(1,12)
            Exception raised:Expected alphaword (at char 12), (line:1, col:13)
            Match alphaword at loc 15(1,16)
            Exception raised:Expected alphaword (at char 15), (line:1, col:16)

        The output shown is that produced by the default debug actions - custom debug actions can be
        specified using :class:`setDebugActions`. Prior to attempting
        to match the ``wd`` expression, the debugging message ``"Match <exprname> at loc <n>(<line>,<col>)"``
        is shown. Then if the parse succeeds, a ``"Matched"`` message is shown, or an ``"Exception raised"``
        message is shown. Also note the use of :class:`setName` to assign a human-readable name to the expression,
        which makes debugging and exception messages easier to understand - for instance, the default
        name created for the :class:`Word` expression without calling ``setName`` is ``"W:(ABCD...)"``.
        """
        if flag:
            self.setDebugActions( _defaultStartDebugAction, _defaultSuccessDebugAction, _defaultExceptionDebugAction )
        else:
            self.debug = False
        return self