Made it more convenient to add frontiers (impedance barriers). These

- at the right place - enable netlist to split a netlist into multiple
smaller netlists. 
Side mark: The "old" discrete system assumed such a device in every
node. (nw)

src/emu/netlist/devices/net_lib.c

@@ -52,7 +52,7 @@ void nl_initialize_factory(netlist_factory_list_t &factory)
 	ENTRY(VCCS,                 VCCS,                   "-")
 	ENTRY(CCCS,                 CCCS,                   "-")
 	ENTRY(dummy_input,          DUMMY_INPUT,            "-")
-	ENTRY(frontier,             FRONTIER,               "+I,Q")
+	ENTRY(frontier,             FRONTIER_DEV,           "+I,G,Q") 	// not intended to be used directly
 	ENTRY(QBJT_EB,              QBJT_EB,                "model")
 	ENTRY(QBJT_switch,          QBJT_SW,                "model")
 	ENTRY(ttl_input,            TTL_INPUT,              "IN")

src/emu/netlist/devices/nld_system.h

@@ -44,19 +44,26 @@
 #define DUMMY_INPUT(_name)                                                     \
 		NET_REGISTER_DEV(dummy_input, _name)
 
-#define FRONTIER(_name, _IN, _OUT)                                             \
+//FIXME: Usage discouraged, use OPTIMIZE_FRONTIER instead
+#define FRONTIER_DEV(_name, _IN, _G, _OUT)                                     \
 		NET_REGISTER_DEV(frontier, _name)                                      \
 		NET_C(_IN, _name.I)                                                    \
+		NET_C(_G,  _name.G)                                                    \
 		NET_C(_OUT, _name.Q)
 
+#define OPTIMIZE_FRONTIER(_attach, _r_in, _r_out)							   \
+		setup.register_frontier(# _attach, _r_in, _r_out);
+
 #define RES_SWITCH(_name, _IN, _P1, _P2)                                       \
 		NET_REGISTER_DEV(res_sw, _name)                                        \
 		NET_C(_IN, _name.I)                                                    \
 		NET_C(_P1, _name.1)                                                    \
 		NET_C(_P2, _name.2)
+
 /* Default device to hold netlist parameters */
 #define PARAMETERS(_name)                                                      \
 		NET_REGISTER_DEV(netlistparams, _name)
+
 // -----------------------------------------------------------------------------
 // mainclock
 // -----------------------------------------------------------------------------
@@ -207,12 +214,24 @@ protected:
 
 	void start()
 	{
-		register_input("I", m_I);
-		register_output("Q", m_Q);
+		register_param("RIN", m_p_RIN, 1.0e6);
+		register_param("ROUT", m_p_ROUT, 50.0);
+
+		register_input("_I", m_I);
+		register_terminal("I",m_RIN.m_P);
+		register_terminal("G",m_RIN.m_N);
+		connect(m_I, m_RIN.m_P);
+
+		register_output("_Q", m_Q);
+		register_terminal("_OP",m_ROUT.m_P);
+		register_terminal("Q",m_ROUT.m_N);
+		connect(m_Q, m_ROUT.m_P);
 	}
 
 	void reset()
 	{
+		m_RIN.set(1.0 / m_p_RIN.Value(),0,0);
+		m_ROUT.set(1.0 / m_p_ROUT.Value(),0,0);
 	}
 
 	void update()
@@ -221,9 +240,13 @@ protected:
 	}
 
 private:
+	NETLIB_NAME(twoterm) m_RIN;
+	NETLIB_NAME(twoterm) m_ROUT;
 	netlist_analog_input_t m_I;
 	netlist_analog_output_t m_Q;
 
+	netlist_param_double_t m_p_RIN;
+	netlist_param_double_t m_p_ROUT;
 };
 
 // -----------------------------------------------------------------------------

src/emu/netlist/nl_parser.c

@@ -49,6 +49,7 @@ bool netlist_parser::parse(const char *buf, const pstring nlname)
 
 	m_tok_ALIAS = register_token("ALIAS");
 	m_tok_NET_C = register_token("NET_C");
+	m_tok_FRONTIER = register_token("OPTIMIZE_FRONTIER");
 	m_tok_PARAM = register_token("PARAM");
 	m_tok_NET_MODEL = register_token("NET_MODEL");
 	m_tok_INCLUDE = register_token("INCLUDE");
@@ -117,6 +118,8 @@ void netlist_parser::parse_netlist(ATTR_UNUSED const pstring &nlname)
 			net_alias();
 		else if (token.is(m_tok_NET_C))
 			net_c();
+		else if (token.is(m_tok_FRONTIER))
+			frontier();
 		else if (token.is(m_tok_PARAM))
 			netdev_param();
 		else if (token.is(m_tok_NET_MODEL))
@@ -217,6 +220,19 @@ void netlist_parser::net_submodel()
 	m_setup.namespace_pop();
 }
 
+void netlist_parser::frontier()
+{
+	// don't do much
+	pstring attachat = get_identifier();
+	require_token(m_tok_comma);
+	double r_IN = eval_param(get_token());
+	require_token(m_tok_comma);
+	double r_OUT = eval_param(get_token());
+	require_token(m_tok_param_right);
+
+	m_setup.register_frontier(attachat, r_IN, r_OUT);
+}
+
 void netlist_parser::net_include()
 {
 	// don't do much

src/emu/netlist/nl_parser.h

@@ -25,6 +25,7 @@ public:
 	void net_alias();
 	void netdev_param();
 	void net_c();
+	void frontier();
 	void device(const pstring &dev_type);
 	void netdev_netlist_start();
 	void netdev_netlist_end();
@@ -48,6 +49,7 @@ private:
 	token_id_t m_tok_comma;
 	token_id_t m_tok_ALIAS;
 	token_id_t m_tok_NET_C;
+	token_id_t m_tok_FRONTIER;
 	token_id_t m_tok_PARAM;
 	token_id_t m_tok_NET_MODEL;
 	token_id_t m_tok_NETLIST_START;

src/emu/netlist/nl_setup.c

@@ -295,6 +295,36 @@ void netlist_setup_t::register_link(const pstring &sin, const pstring &sout)
 	//  fatalerror("Error adding link %s<==%s to link list\n", sin.cstr(), sout.cstr());
 }
 
+void netlist_setup_t::register_frontier(const pstring attach, const double r_IN, const double r_OUT)
+{
+	static int frontier_cnt = 0;
+	pstring frontier_name = pstring::sprintf("frontier_%d", frontier_cnt);
+	frontier_cnt++;
+	netlist_device_t *front = register_dev("nld_frontier", frontier_name);
+	register_param(frontier_name + ".RIN", r_IN);
+	register_param(frontier_name + ".ROUT", r_OUT);
+	register_link(frontier_name + ".G", "GND");
+	pstring attfn = build_fqn(attach);
+	bool found = false;
+	for (std::size_t i = 0; i < m_links.size(); i++)
+	{
+		if (m_links[i].e1 == attfn)
+		{
+			m_links[i].e1 = front->name() + ".I";
+			found = true;
+		}
+		else if (m_links[i].e2 == attfn)
+		{
+			m_links[i].e2 = front->name() + ".I";
+			found = true;
+		}
+	}
+	if (!found)
+		netlist().error("Frontier setup: found no occurrence of %s\n", attach.cstr());
+	register_link(attach, frontier_name + ".Q");
+}
+
+
 void netlist_setup_t::register_param(const pstring &param, const double value)
 {
 	// FIXME: there should be a better way

src/emu/netlist/nl_setup.h

@@ -151,6 +151,7 @@ public:
 	void register_link(const pstring &sin, const pstring &sout);
 	void register_param(const pstring &param, const pstring &value);
 	void register_param(const pstring &param, const double value);
+	void register_frontier(const pstring attach, const double r_IN, const double r_OUT);
 
 	void register_object(netlist_device_t &dev, const pstring &name, netlist_object_t &obj);
 	bool connect(netlist_core_terminal_t &t1, netlist_core_terminal_t &t2);

src/emu/netlist/plib/pparser.c

@@ -267,6 +267,7 @@ ATTR_COLD void ptokenizer::error(const char *format, ...)
 
 ppreprocessor::ppreprocessor()
 {
+	m_expr_sep.add("!");
 	m_expr_sep.add("(");
 	m_expr_sep.add(")");
 	m_expr_sep.add("+");
@@ -294,11 +295,20 @@ double ppreprocessor::expr(const pstring_list_t &sexpr, std::size_t &start, int
 	if (tok == "(")
 	{
 		start++;
-		val = expr(sexpr, start, prio);
+		val = expr(sexpr, start, /*prio*/ 0);
 		if (sexpr[start] != ")")
 			error("parsing error!");
 		start++;
 	}
+	else if (tok == "!")
+	{
+		start++;
+		val = expr(sexpr, start, 90);
+		if (val != 0)
+			val = 0;
+		else
+			val = 1;
+	}
 	else
 	{
 		tok=sexpr[start];

src/emu/netlist/tools/nl_convert.c

@@ -5,8 +5,30 @@
  *
  */
 
+#include <algorithm>
+
 #include "nl_convert.h"
 
+template<typename Class>
+static plist_t<int> bubble(const pnamedlist_t<Class *> &sl)
+{
+	plist_t<int> ret(sl.size());
+	for (int i=0; i<sl.size(); i++)
+		ret[i] = i;
+
+	for(int i=0; i < sl.size()-1;i++)
+    {
+        for(int j=i+1; j < sl.size(); j++)
+        {
+            if(sl[ret[i]]->name() > sl[ret[j]]->name())
+            {
+            	std::swap(ret[i], ret[j]);
+            }
+        }
+    }
+	return ret;
+}
+
 /*-------------------------------------------------
     convert - convert a spice netlist
 -------------------------------------------------*/
@@ -72,17 +94,20 @@ void nl_convert_base_t::dump_nl()
 		if (net->terminals().size() == 1)
 			net->set_no_export();
 	}
+	plist_t<int> sorted = bubble(m_devs);
 	for (std::size_t i=0; i<m_devs.size(); i++)
 	{
-		if (m_devs[i]->has_value())
-			out("%s(%s, %s)\n", m_devs[i]->type().cstr(),
-					m_devs[i]->name().cstr(), get_nl_val(m_devs[i]->value()).cstr());
-		else if (m_devs[i]->has_model())
-			out("%s(%s, \"%s\")\n", m_devs[i]->type().cstr(),
-					m_devs[i]->name().cstr(), m_devs[i]->model().cstr());
+		std::size_t j = sorted[i];
+
+		if (m_devs[j]->has_value())
+			out("%s(%s, %s)\n", m_devs[j]->type().cstr(),
+					m_devs[j]->name().cstr(), get_nl_val(m_devs[j]->value()).cstr());
+		else if (m_devs[j]->has_model())
+			out("%s(%s, \"%s\")\n", m_devs[j]->type().cstr(),
+					m_devs[j]->name().cstr(), m_devs[j]->model().cstr());
 		else
-			out("%s(%s)\n", m_devs[i]->type().cstr(),
-					m_devs[i]->name().cstr());
+			out("%s(%s)\n", m_devs[j]->type().cstr(),
+					m_devs[j]->name().cstr());
 	}
 	// print nets
 	for (std::size_t i=0; i<m_nets.size(); i++)