[{"_1":2,"_53":-5,"_54":-5},"loaderData",{"_3":4,"_7":8,"_52":-5},"root",{"_5":6},"path","/blogs/tags/lexical-analysis","pages/Tag",{"_9":10,"_48":49,"_19":25,"_50":51},"posts",[11],{"_12":13,"_14":15,"_16":17,"_19":20,"_26":27,"_28":29,"_30":31,"_34":35,"_38":39,"_40":41},"id","clzs3zz092d6x07pnpn0umma5","publishDate","2024-08-06","category",[18],"tutorial","tag",[21,22,23,24,25],"c++","game-development","scripting-language","game-engine","lexical-analysis","slug","developing-a-custom-scripting-language-for-your-game-engine-in-c","title","Developing a Custom Scripting Language for Your Game Engine in C++","excerpt",{"_32":33},"text","Learn how to create a custom scripting language for your game engine using C++. This guide covers designing the language, tokenizing input, parsing it into an abstract syntax tree, and executing script commands. Enhance your game's flexibility and control with this step-by-step tutorial.","coverImg",{"_36":37},"url","https://ap-south-1.graphassets.com/AHDh3MjtFRAmkhgRu025Qz/TFlKlpEbQAOkNqtjP5xm","content","***Creating a custom scripting language for your game engine can give you flexibility and control over your game's behavior without recompiling the entire engine. This guide will walk you through the steps to design, parse, and execute a simple scripting language in C++.***\n\n# Introduction\n\nIn this guide, we'll create a basic scripting language for our game engine. The scripting language will support simple operations like variable assignment, arithmetic operations, and printing values to the console.\n\nIf you're unfamilier with a game engine, read [creating a game engine with c++ and OpenGL](/blogs/tutorial/creating-a-game-engine-with-c-and-opengl-a-step-by-step-guide).\n\n# Designing the Scripting Language\n\nFirst, we need to define the syntax and features of our scripting language. Let's keep it simple:\n- Variables: `var x = 10`\n- Arithmetic: `x = x + 5`\n- Print: `print(x)`\n\n# Lexical Analysis (Tokenization)\n\nWe'll start by breaking the script into tokens. Each token represents a keyword, identifier, operator, or literal value.\n\n## Tokenizer Implementation\n\nCreate a new file `tokenizer.h`:\n\n```cpp\n#ifndef TOKENIZER_H\n#define TOKENIZER_H\n\n#include \n#include \n\nenum class TokenType {\n VAR,\n IDENTIFIER,\n NUMBER,\n ASSIGN,\n PLUS,\n PRINT,\n END,\n UNKNOWN\n};\n\nstruct Token {\n TokenType type;\n std::string value;\n};\n\nstd::vector tokenize(const std::string& code);\n\n#endif // TOKENIZER_H\n```\n\nNow, implement the tokenizer in `tokenizer.cpp`:\n\n```cpp\n#include \"tokenizer.h\"\n#include \n#include \n\nstd::vector tokenize(const std::string& code) {\n std::vector tokens;\n std::istringstream stream(code);\n std::string word;\n\n while (stream >> word) {\n if (word == \"var\") {\n tokens.push_back({ TokenType::VAR, word });\n } else if (word == \"print\") {\n tokens.push_back({ TokenType::PRINT, word });\n } else if (word == \"=\") {\n tokens.push_back({ TokenType::ASSIGN, word });\n } else if (word == \"+\") {\n tokens.push_back({ TokenType::PLUS, word });\n } else if (std::isdigit(word[0])) {\n tokens.push_back({ TokenType::NUMBER, word });\n } else {\n tokens.push_back({ TokenType::IDENTIFIER, word });\n }\n }\n\n tokens.push_back({ TokenType::END, \"\" });\n return tokens;\n}\n```\n\n## Parsing the Script\nNext, we'll parse the tokens into an abstract syntax tree (AST).\n\nParser Implementation\nCreate a new file `parser.h`:\n\n```cpp\n#ifndef PARSER_H\n#define PARSER_H\n\n#include \"tokenizer.h\"\n#include \n#include \n\nclass ASTNode {\npublic:\n virtual ~ASTNode() = default;\n virtual void execute(std::unordered_map& variables) const = 0;\n};\n\nusing ASTNodePtr = std::unique_ptr;\n\nASTNodePtr parse(const std::vector& tokens);\n\n#endif // PARSER_H\n```\n\nImplement the parser in `parser.cpp`:\n\n```cpp\n#include \"parser.h\"\n#include \n\nclass VarNode : public ASTNode {\n std::string name;\n int value;\npublic:\n VarNode(const std::string& name, int value) : name(name), value(value) {}\n void execute(std::unordered_map& variables) const override {\n variables[name] = value;\n }\n};\n\nclass PrintNode : public ASTNode {\n std::string name;\npublic:\n PrintNode(const std::string& name) : name(name) {}\n void execute(std::unordered_map& variables) const override {\n std::cout << variables[name] << std::endl;\n }\n};\n\nclass AssignNode : public ASTNode {\n std::string name;\n int value;\npublic:\n AssignNode(const std::string& name, int value) : name(name), value(value) {}\n void execute(std::unordered_map& variables) const override {\n variables[name] = value;\n }\n};\n\nASTNodePtr parse(const std::vector& tokens) {\n auto it = tokens.begin();\n if (it->type == TokenType::VAR) {\n ++it;\n std::string name = it->value;\n ++it;\n ++it; // Skip '='\n int value = std::stoi(it->value);\n return std::make_unique(name, value);\n } else if (it->type == TokenType::PRINT) {\n ++it;\n return std::make_unique(it->value);\n } else if (it->type == TokenType::IDENTIFIER) {\n std::string name = it->value;\n ++it;\n ++it; // Skip '='\n int value = std::stoi(it->value);\n return std::make_unique(name, value);\n }\n throw std::runtime_error(\"Unknown statement\");\n}\n```\n\n## Executing the Script\nFinally, we'll execute the AST nodes.\n\n** Main Implementation **\nCreate a new file main.cpp:\n\n```cpp\n#include \"tokenizer.h\"\n#include \"parser.h\"\n#include \n#include \n\nint main() {\n std::string code = \"var x = 10\\nprint(x)\\nx = x + 5\\nprint(x)\";\n \n auto tokens = tokenize(code);\n std::unordered_map variables;\n \n for (const auto& token : tokens) {\n if (token.type == TokenType::END) break;\n auto node = parse(tokens);\n node->execute(variables);\n }\n \n return 0;\n}\n```\n## Putting It All Together\n\nTo compile and run your script, use a `Makefile`:\n\n```makefile\nall: main\n\nmain: main.o tokenizer.o parser.o\n g++ -o main main.o tokenizer.o parser.o\n\nmain.o: main.cpp tokenizer.h parser.h\n g++ -c main.cpp\n\ntokenizer.o: tokenizer.cpp tokenizer.h\n g++ -c tokenizer.cpp\n\nparser.o: parser.cpp parser.h tokenizer.h\n g++ -c parser.cpp\n\nclean:\n rm -f *.o main\n```\n\n**Run the following commands to build and execute the program:**\n\n```sh\nmake\n./main\n```\n\n# Conclusion\nIn this guide, we developed a simple scripting language for a game engine in C++. While the language and interpreter are basic, they serve as a foundation for more complex features. You can extend this project by adding more operations, control structures (like loops and conditionals), and improving error handling.\n\nHappy coding!","author",{"_42":43,"_44":45,"_46":47},"name","Dexter","img","https://avatars.githubusercontent.com/u/71167911?v=4","social","https://github.com/dexter-xD","hasMorePosts",false,"page",1,"layouts/HomeLayout","actionData","errors"]