+dnl Configure options.
+AC_ARG_ENABLE(html-doc, [ --enable-html-doc build HTML documentation [default=yes]], , enable_html_doc=yes)
+AC_ARG_ENABLE(ps-doc, [ --enable-ps-doc build PostScript documentation [default=yes]], , enable_ps_doc=yes)
+AC_ARG_WITH(cint, [ --with-cint=CINTSYSDIR build GiNaC-cint C++ interpreter [default=no]], , with_cint=no)
+
+dnl Check for data types which are needed by the hash function (golden_ratio_hash).