Enhance the interactive interpreter mode of dfusion.

1. Reimplement Console.print* to behave exactly as the standard print
   function, and apply print = Console.println from c++ init code.
2. Add a couple of convenience shortcuts to save some manual typing
   when poking around data structures using the interactive prompt.
3. Change the prompt string to a more distinguished shape.

plugins/Dfusion/dfusion.cpp

@@ -64,6 +64,11 @@ DFhackCExport command_result plugin_init ( Core * c, std::vector <PluginCommand>
 		st.setglobal("WINDOWS");
 	#endif
 
+    st.getglobal("Console");
+    st.getfield("println");
+    st.setglobal("print");
+    st.pop();
+
     commands.push_back(PluginCommand("dfusion","Run dfusion system (interactive i.e. can input further commands).",dfusion,true));
 	commands.push_back(PluginCommand("dfuse","Init dfusion system (not interactive).",dfuse,false));
 	commands.push_back(PluginCommand("lua", "Run interactive interpreter. Use 'lua <filename>' to run <filename> instead.",lua_run,true));
@@ -115,27 +120,74 @@ void InterpreterLoop(color_ostream &out)
 	DFHack::CommandHistory hist;
 	lua::state s=lua::glua::Get();
 	string curline;
-	out.print("Type quit to exit interactive mode\n");
+	out.print("Type quit to exit interactive mode.\n"
+              "Shortcuts:\n"
+              " '= foo' => '_1,_2,... = foo'\n"
+              " '! foo' => 'print(foo)'\n");
 	assert(out.is_console());
 	Console &con = static_cast<Console&>(out);
-	con.lineedit(">>",curline,hist);
+	int vcnt = 1;
+
+    s.settop(0);
+
+    for (;;) {
+        con.lineedit("[lua]# ",curline,hist);
+
+        if (curline.empty())
+            continue;
+        if (curline == "quit")
+            break;
 
-	while (curline!="quit") {
 		hist.add(curline);
+
 		try
+		{
+            if (curline[0] == '=')
+            {
+                curline = "return " + curline.substr(1);
+
+                s.loadstring(curline);
+                s.pcall(0, LUA_MULTRET);
+                int numret = s.gettop();
+
+                for (int i = 1; i <= numret; i++)
+                {
+                    if (i == 1)
+                    {
+                        s.pushvalue(i);
+                        s.setglobal("_");
+                    }
+
+                    std::string name = stl_sprintf("_%d", vcnt++);
+                    s.pushvalue(i);
+                    s.setglobal(name);
+
+                    con.print("%s = ", name.c_str());
+                    s.getglobal("print");
+                    s.pushvalue(i);
+                    s.pcall(1,0);
+                }
+            }
+            else if (curline[0] == '!')
+            {
+                curline = "print(" + curline.substr(1) + ")";
+                s.loadstring(curline);
+                s.pcall();
+            }
+            else
             {
                 s.loadstring(curline);
                 s.pcall();
+            }
 		}
 		catch(lua::exception &e)
 		{
 			con.printerr("Error:%s\n",e.what());
             con.printerr("%s\n",lua::DebugDump(lua::glua::Get()).c_str());
-			s.settop(0);
-		}
-		con.lineedit(">>",curline,hist);
 		}
+
         s.settop(0);
+	}
 }
 command_result lua_run_file (color_ostream &out, std::vector <std::string> &parameters)
 {

plugins/Dfusion/luafiles/init.lua

@@ -1,6 +1,3 @@
-function print(msg)
-	Console.print(msg.."\n")
-end
 function err(msg) --make local maybe...
 	print(msg)
 	print(debug.traceback())

plugins/Dfusion/src/lua_Console.cpp

@@ -1,4 +1,7 @@
 #include "lua_Console.h"
+
+#include <sstream>
+
 //TODO error management. Using lua error? or something other?
 static DFHack::color_ostream* GetConsolePtr(lua::state &st)
 {
@@ -9,21 +12,52 @@ static DFHack::color_ostream* GetConsolePtr(lua::state &st)
 	st.settop(t);
 	return c;
 }
+
+static std::string lua_print_fmt(lua_State *L)
+{
+    /* Copied from lua source to fully replicate builtin print */
+    int n = lua_gettop(L);  /* number of arguments */
+    lua_getglobal(L, "tostring");
+
+    std::stringstream ss;
+
+    for (int i=1; i<=n; i++) {
+        lua_pushvalue(L, -1);  /* function to be called */
+        lua_pushvalue(L, i);   /* value to print */
+        lua_call(L, 1, 1);
+        const char *s = lua_tostring(L, -1);  /* get result */
+        if (s == NULL)
+            luaL_error(L, "tostring must return a string to print");
+        if (i>1)
+            ss << '\t';
+        ss << s;
+        lua_pop(L, 1);  /* pop result */
+    }
+
+    return ss.str();
+}
+
 static int lua_Console_print(lua_State *S)
 {
     lua::state st(S);
-	int t=st.gettop();
     DFHack::color_ostream* c=GetConsolePtr(st);
-	c->print("%s",st.as<string>(t).c_str());
+    c->print("%s", lua_print_fmt(S).c_str());
+    return 0;
+}
+
+static int lua_Console_println(lua_State *S)
+{
+    lua::state st(S);
+    DFHack::color_ostream* c=GetConsolePtr(st);
+    c->print("%s\n", lua_print_fmt(S).c_str());
     return 0;
 }
 
 static int lua_Console_printerr(lua_State *S)
 {
     lua::state st(S);
-	int t=st.gettop();
     DFHack::color_ostream* c=GetConsolePtr(st);
-	c->printerr("%s",st.as<string>(t).c_str());
+    c->printerr("%s", lua_print_fmt(S).c_str());
     return 0;
 }
 
@@ -123,6 +157,7 @@ static int lua_Console_lineedit(lua_State *S)
 const luaL_Reg lua_console_func[]=
 {
 	{"print",lua_Console_print},
+    {"println",lua_Console_println},
 	{"printerr",lua_Console_printerr},
 	{"clear",lua_Console_clear},
 	{"gotoxy",lua_Console_gotoxy},