https://svn.boost.org/trac10/ticket/2960 <p> Due to a bug (or perhaps my misusage), I am unable to compose two argument packs, each formed using positional arguments, using the comma operator. </p> <p> <a class="ext-link" href="news://news.gmane.org:119/grtmb9$tpq$1@ger.gmane.org"><span class="icon">​</span>news://news.gmane.org:119/grtmb9$tpq$1@ger.gmane.org</a> Compiler : i686-apple-darwin9-gcc-4.0.1 </p> <p> BOOST_PARAMETER_KEYWORD(tag, x) BOOST_PARAMETER_KEYWORD(tag, y) template&lt;class <a class="missing wiki">ArgumentPack</a>&gt; void f(<a class="missing wiki">ArgumentPack</a> const &amp; args){ </p> <blockquote> <p> double x_val = args[x]; double y_val = args[y]; </p> </blockquote> <p> } </p> <blockquote> <p> typedef boost::parameter::parameters&lt; </p> <blockquote> <p> parameter::required&lt;tag::x&gt; </p> <blockquote class="citation"> <p> par_x_t; </p> </blockquote> </blockquote> <p> typedef boost::parameter::parameters&lt; </p> <blockquote> <p> parameter::required&lt;tag::y&gt; </p> <blockquote class="citation"> <p> par_y_t; </p> </blockquote> </blockquote> </blockquote> <blockquote> <blockquote> <p> double x_val = 9.0; double y_val = 0.1; spec_x_t spec_x; spec_y_t spec_y; f( </p> <blockquote> <p> ( spec_x(x_val),spec_y(y_val)) </p> </blockquote> <p> ); <em>no match operator[&lt;unnamed&gt;::x] </em></p> </blockquote> </blockquote> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/2960 Trac 1.4.3