Last active
January 24, 2026 21:48
-
-
Save Garciat/dae707beb822d191447ce9dcdb61ab61 to your computer and use it in GitHub Desktop.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| #include <memory> | |
| #include <print> | |
| #include <sstream> | |
| #include <string> | |
| #include <variant> | |
| template<class... Ts> | |
| struct overloaded : Ts... { using Ts::operator()...; }; | |
| auto format(auto&& value) { | |
| std::ostringstream os; | |
| os << value; | |
| return os.str(); | |
| } | |
| template <typename... Ts> | |
| auto format(std::variant<Ts...> v) { | |
| return std::visit([](auto&& item) -> auto { | |
| return format(item); | |
| }, v); | |
| } | |
| template <typename T> | |
| T formula(T x, T y) { | |
| return 10 + x * 8 + x * y + 5; | |
| } | |
| template <typename T> | |
| using Ptr = std::shared_ptr<T>; | |
| struct Expr { | |
| struct Var { std::string name; }; | |
| struct Add { Ptr<Expr> lhs, rhs; }; | |
| struct Mul { Ptr<Expr> lhs, rhs; }; | |
| struct Lit { std::variant<int, double> value; }; | |
| std::variant<Var, Add, Mul, Lit> data; | |
| static Ptr<Expr> var(std::string name) { | |
| return std::make_shared<Expr>(Expr{Var{name}}); | |
| } | |
| static Ptr<Expr> add(Ptr<Expr> lhs, Ptr<Expr> rhs) { | |
| return std::make_shared<Expr>(Expr{Add{lhs, rhs}}); | |
| } | |
| static Ptr<Expr> mul(Ptr<Expr> lhs, Ptr<Expr> rhs) { | |
| return std::make_shared<Expr>(Expr{Mul{lhs, rhs}}); | |
| } | |
| static Ptr<Expr> lit(decltype(Lit::value) item) { | |
| return std::make_shared<Expr>(Expr{Lit{item}}); | |
| } | |
| }; | |
| std::string pp(Ptr<Expr> expr) { | |
| return std::visit(overloaded{ | |
| [](Expr::Var var) -> std::string { | |
| return var.name; | |
| }, | |
| [](Expr::Add add) -> std::string { | |
| return "(" + pp(add.lhs) + " + " + pp(add.rhs) + ")"; | |
| }, | |
| [](Expr::Mul mul) -> std::string { | |
| return "(" + pp(mul.lhs) + " + " + pp(mul.rhs) + ")"; | |
| }, | |
| [](Expr::Lit lit) -> std::string { | |
| return format(lit.value); | |
| }, | |
| }, expr->data); | |
| } | |
| Ptr<Expr> operator+(Ptr<Expr> lhs, Ptr<Expr> rhs) { | |
| return Expr::add(lhs, rhs); | |
| } | |
| Ptr<Expr> operator*(Ptr<Expr> lhs, Ptr<Expr> rhs) { | |
| return Expr::mul(lhs, rhs); | |
| } | |
| template <typename T> | |
| Ptr<Expr> operator+(Ptr<Expr> lhs, T rhs) { | |
| return Expr::add(lhs, Expr::lit(rhs)); | |
| } | |
| template <typename T> | |
| Ptr<Expr> operator+(T lhs, Ptr<Expr> rhs) { | |
| return Expr::add(Expr::lit(lhs), rhs); | |
| } | |
| template <typename T> | |
| Ptr<Expr> operator*(Ptr<Expr> lhs, T rhs) { | |
| return Expr::mul(lhs, Expr::lit(rhs)); | |
| } | |
| template <typename T> | |
| Ptr<Expr> operator*(T lhs, Ptr<Expr> rhs) { | |
| return Expr::mul(Expr::lit(lhs), rhs); | |
| } | |
| int main() { | |
| std::println("{}", pp(formula(Expr::var("x"), Expr::var("y")))); | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment