 second and third <i>required</i> parameters.&nbsp;
			These two boundaries are either passed through <b>BOOST_PP_ITERATION_LIMITS</b> <i>or</i> as part of <b>BOOST_PP_ITERATION_PARAMS_<i>x</i></b>.
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			Optionally, a fourth parameter may be passed that associates flags with an iteration.&nbsp;
			These flags are primarily useful to distinguish one iteration from another in the same file.&nbsp;
			This parameter can only be passed through <b>BOOST_PP_ITERATION_PARAMS_<i>x</i></b>.
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