2 files changed, 98 insertions, 5 deletions

diff --git a/src/MoonP/moon_parser.cpp b/src/MoonP/moon_parser.cpp
index 872e30e..58f8fb3 100644
--- a/src/MoonP/moon_parser.cpp
+++ b/src/MoonP/moon_parser.cpp
@@ -646,7 +646,7 @@ std::string ParseInfo::errorMessage(std::string_view msg, const input_range* loc
         int oldCol = loc->m_begin.m_col;
         int col = std::max(0, oldCol - 1);
         auto it = begin;
-        for (int i = 0; i < oldCol; ++i) {
+        for (int i = 0; i < oldCol && it != end; ++i) {
                 if (*it > ASCII) {
                         ++col;
                 }
diff --git a/src/moonp.cpp b/src/moonp.cpp
index fd9548a..d1c565f 100644
--- a/src/moonp.cpp
+++ b/src/moonp.cpp
@@ -11,6 +11,8 @@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLI
 
 #include <iostream>
 #include <iomanip>
+#include <cstdlib>
+#include <limits>
 #include <fstream>
 #include <chrono>
 #include <future>
@@ -49,6 +51,25 @@ void pushMoonp(lua_State* L, std::string_view name) {
         lua_pop(L, 3); // item
 }
 
+void pushOptions(lua_State* L, int lineOffset) {
+        lua_newtable(L);
+        lua_pushliteral(L, "lint_global");
+        lua_pushboolean(L, 0);
+        lua_rawset(L, -3);
+        lua_pushliteral(L, "implicit_return_root");
+        lua_pushboolean(L, 1);
+        lua_rawset(L, -3);
+        lua_pushliteral(L, "reserve_line_number");
+        lua_pushboolean(L, 1);
+        lua_rawset(L, -3);
+        lua_pushliteral(L, "same_module");
+        lua_pushboolean(L, 1);
+        lua_rawset(L, -3);
+        lua_pushliteral(L, "line_offset");
+        lua_pushinteger(L, lineOffset);
+        lua_rawset(L, -3);
+}
+
 int main(int narg, const char** args) {
         const char* help =
 "Usage: moonp [options|files|directories] ...\n\n"
@@ -61,9 +82,76 @@ int main(int narg, const char** args) {
 "   -l       Write line numbers from source codes\n"
 "   -v       Print version\n"
 "   --       Read from standard in, print to standard out\n"
-"            (Must be first and only argument)\n";
-        if (narg == 0) {
-                std::cout << help;
+"            (Must be first and only argument)\n\n"
+"   Execute without options to enter REPL, type symbol '$'\n"
+"   in a single line to start/stop multi-line mode\n";
+        if (narg == 1) {
+                lua_State* L = luaL_newstate();
+                openlibs(L);
+                DEFER(lua_close(L));
+                pushMoonp(L, "insert_loader"sv);
+                if (lua_pcall(L, 0, 0, 0) != 0) {
+                        std::cout << lua_tostring(L, -1) << '\n';
+                        return 1;
+                }
+                int count = 0;
+                while (!std::cin.fail()) {
+                        count++;
+                        std::cout << "moon> "sv;
+                        std::string codes;
+                        std::getline(std::cin, codes);
+                        MoonP::Utils::trim(codes);
+                        if (codes == "$"sv) {
+                                codes.clear();
+                                for (std::string line; std::getline(std::cin, line);) {
+                                        auto temp = line;
+                                        MoonP::Utils::trim(temp);
+                                        if (temp == "$"sv) {
+                                                break;
+                                        }
+                                        codes += '\n';
+                                        codes += line;
+                                }
+                        }
+                        codes.insert(0, "global *\n"sv);
+                        int top = lua_gettop(L);
+                        DEFER(lua_settop(L, top));
+                        pushMoonp(L, "loadstring"sv);
+                        lua_pushlstring(L, codes.c_str(), codes.size());
+                        lua_pushstring(L, (std::string("=(repl:") + std::to_string(count) + ')').c_str());
+                        pushOptions(L, -1);
+                        const std::string_view Err = "\033[35m"sv, Val = "\033[33m"sv, Stop = "\033[0m\n"sv;
+                        if (lua_pcall(L, 3, 2, 0) != 0) {
+                                std::cout << Err << lua_tostring(L, -1) << Stop;
+                                continue;
+                        }
+                        if (lua_isnil(L, -2) != 0) {
+                                std::cout << Err << lua_tostring(L, -1) << Stop;
+                                continue;
+                        }
+                        lua_pop(L, 1);
+                        pushMoonp(L, "pcall"sv);
+                        lua_insert(L, -2);
+                        int last = lua_gettop(L) - 2;
+                        if (lua_pcall(L, 1, LUA_MULTRET, 0) != 0) {
+                                std::cout << Err << lua_tostring(L, -1) << Stop;
+                                continue;
+                        }
+                        int cur = lua_gettop(L);
+                        int retCount = cur - last;
+                        bool success = lua_toboolean(L, -retCount) != 0;
+                        if (success) {
+                                if (retCount > 1) {
+                                        for (int i = 1; i < retCount; ++i) {
+                                                std::cout << Val << luaL_tolstring(L, -retCount + i, nullptr) << Stop;
+                                                lua_pop(L, 1);
+                                        }
+                                }
+                        } else {
+                                std::cout << Err << lua_tostring(L, -1) << Stop;
+                        }
+                }
+                std::cout << '\n';
                 return 0;
         }
         MoonP::MoonConfig config;
@@ -129,10 +217,15 @@ int main(int narg, const char** args) {
                                         lua_pushlstring(L, evalStr.c_str(), evalStr.size());
                                         lua_pushliteral(L, "=(eval str)");
                                 }
-                                if (lua_pcall(L, 2, 1, 0) != 0) {
+                                if (lua_pcall(L, 2, 2, 0) != 0) {
+                                        std::cout << lua_tostring(L, -1) << '\n';
+                                        return 1;
+                                }
+                                if (lua_isnil(L, -2) != 0) {
                                         std::cout << lua_tostring(L, -1) << '\n';
                                         return 1;
                                 }
+                                lua_pop(L, 1);
                                 pushMoonp(L, "pcall"sv);
                                 lua_insert(L, -2);
                                 if (lua_pcall(L, 1, 2, 0) != 0) {