No, really, this is the code for the new keyword parsing.

luprex/core/cpp/luastack.hpp

@@ -155,6 +155,8 @@
 #define LUASTACK_HPP
 
 #include "wrap-string.hpp"
+#include "wrap-set.hpp"
+#include <cstring>
 
 extern "C" {
 #include "lua.h"
@@ -351,6 +353,8 @@ private:
     static void delete_pointer(void *p) { delete (T*)p; }
     static void do_not_delete(void *p) { }
 
+    void argerr(const char *arg, const char *tp) const;
+
 public:
     template<class... SS>
     LuaStack(lua_State *L, SS & ... stackslots) {
@@ -386,19 +390,22 @@ public:
     bool isint(LuaSlot s) const;
     bool isthread(LuaSlot s) const { return lua_type(L_, s) == LUA_TTHREAD; }
     bool isfunction(LuaSlot s) const { return lua_type(L_, s) == LUA_TFUNCTION; }
+    bool iscfunction(LuaSlot s) const { return lua_iscfunction(L_, s) != 0; }
     bool isboolean(LuaSlot s) const { return lua_type(L_, s) == LUA_TBOOLEAN; }
     bool isnil(LuaSlot s) const { return lua_type(L_, s) == LUA_TNIL; }
-    bool iscfunction(LuaSlot s) const { return lua_iscfunction(L_, s) != 0; }
     bool istoken(LuaSlot s) const { return lua_islightuserdata(L_, s) != 0; }
 
-    void checktable(LuaSlot index) const { checktype(index, LUA_TTABLE); }
-    void checkstring(LuaSlot index) const { checktype(index, LUA_TSTRING); }
-    void checknumber(LuaSlot index) const { checktype(index, LUA_TNUMBER); }
-    void checkthread(LuaSlot index) const { checktype(index, LUA_TTHREAD); }
-    void checkfunction(LuaSlot index) const { checktype(index, LUA_TFUNCTION); }
-    void checkboolean(LuaSlot index) const { checktype(index, LUA_TBOOLEAN); }
-    void checknil(LuaSlot index) const { checktype(index, LUA_TNIL); }
-    void checktoken(LuaSlot index) const { checktype(index, LUA_TLIGHTUSERDATA); }
+    void checktable(LuaSlot s, const char *n) const { if (!istable(s)) argerr(n, "table"); }
+    void checkstring(LuaSlot s, const char *n) const { if (!isstring(s)) argerr(n, "string"); }
+    void checknumber(LuaSlot s, const char *n) const { if (!isnumber(s)) argerr(n, "number"); }
+    void checkinteger(LuaSlot s, const char *n) const { if (!isinteger(s)) argerr(n, "integer"); }
+    void checkint(LuaSlot s, const char *n) const { if (!isint(s)) argerr(n, "int"); }
+    void checkthread(LuaSlot s, const char *n) const { if (!isthread(s)) argerr(n, "thread"); }
+    void checkfunction(LuaSlot s, const char *n) const { if (!isfunction(s)) argerr(n, "function"); }
+    void checkcfunction(LuaSlot s, const char *n) const { if (!iscfunction(s)) argerr(n, "cfunction"); }
+    void checkboolean(LuaSlot s, const char *n) const { if (!isboolean(s)) argerr(n, "boolean"); }
+    void checknil(LuaSlot s, const char *n) const { if (!isnil(s)) argerr(n, "nil"); }
+    void checktoken(LuaSlot s, const char *n) const { if (!istoken(s)) argerr(n, "token"); }
     
     bool ckboolean(LuaSlot s) const;
     lua_Integer ckinteger(LuaSlot s) const;
@@ -516,6 +523,37 @@ public:
     static bool int64_storable(int64_t v) { return (v <= MAXINT) && (v >= -MAXINT); }
 };
 
+// This is a helper class to help parse tables full of keywords.
+class LuaKeywordParser {
+    struct cmp_char {
+        bool operator () (const char *s1, const char *s2) const {
+            return strcmp(s1, s2) < 0;
+        };
+    };
+private:
+    lua_State *L_;
+    int slot_;
+    eng::set<const char *, cmp_char> parsed_;
+
+    void init(const lua_State *L, int slot);
+public:
+    // The constructor will throw a lua error if the
+    // slot is not a table.
+    LuaKeywordParser(lua_State *L, int slot);
+    LuaKeywordParser(const LuaStack &LS, LuaSlot slot) : LuaKeywordParser(LS.state(), slot.index()) {}
+
+    // Fetch a value from the table.  This never throws.
+    // Return true if the value is non-nil.
+    bool parse(LuaSlot slot, const char *kw);
+
+    // Check if there are any keywords in the table that
+    // were never parsed.  If so, throw an error.
+    void check_unparsed_keywords();
+
+    // Fetch the state pointer. 
+    lua_State *state() const { return L_; }
+};
+
 class LuaConstantReg : public eng::nevernew {
 private:
     const char *name_;

luprex/core/cpp/planemap.hpp

@@ -131,8 +131,8 @@ public:
     
     // Convert a lua table into a scan configuration.
     //
-    // If there is an error in the configuration, returns an
-    // error message, otherwise returns empty string.
+    // If there is an error in the configuration, 
+    // throws a lua error message.
     //
     // Caution: if this detects the configuration flag 'near',
     // then it stores the near ID.  However, it doesn't fetch
@@ -141,7 +141,7 @@ public:
     // and plane.  This is admittedly ugly, but it eliminates
     // a dependency on the world module.
     //
-    eng::string configure(const LuaStack &LS, LuaSlot slot);
+    void configure(LuaKeywordParser &kw);
 
     void set_bbox_given_center_radius(const util::XYZ &center, float r) {
         set_center(center);