source: doc/generic_types/evaluation/object.hpp @ 3fb7f5e

#pragma once

#include <cstddef>
#include <exception>
#include <iomanip>
#include <memory>
#include <ostream>
#include <string>
#include <typeinfo>
#include <typeindex>

class bad_cast : public std::exception {
        std::string why;
public:
        bad_cast( const std::type_index& f, const std::type_index& t ) : std::exception() {
                why = std::string{"bad cast of "} + f.name() + " to " + t.name();
        }

        ~bad_cast() override = default;
        
        const char* what() const noexcept override { return why.c_str(); }
};

template<typename T>
std::type_index class_of() { return { typeid(T) }; }

class object {
public:
        std::type_index get_class() const { return { this ? typeid(*this) : typeid(std::nullptr_t) }; }

        template<typename T>
        T& as() {
                T* p = dynamic_cast<T*>(this);
                if ( !p ) throw bad_cast{ get_class(), class_of<T>() };
                return *p;
        }

        template<typename T>
        const T& as() const {
                const T* p = dynamic_cast<const T*>(this);
                if ( !p ) throw bad_cast{ get_class(), class_of<T>() };
                return *p;
        }

        virtual std::unique_ptr<object> new_inst() const = 0;
        
        virtual std::unique_ptr<object> new_copy() const = 0;
        
        virtual object& operator= (const object&) = 0;
        
        virtual ~object() = default;
};

template<typename To, typename From>
std::unique_ptr<To> as_ptr( std::unique_ptr<From>&& p ) {
        return std::unique_ptr<To>{ &p.release()->template as<To>() };
}

class ordered : public virtual object {
public:
        virtual int cmp(const ordered&) const = 0;

        bool operator< (const ordered& that) const { return cmp(that) < 0; }

        bool operator<= ( const ordered& that ) const { return cmp(that) <= 0; }

        bool operator== ( const ordered& that ) const { return cmp(that) == 0; }

        bool operator!= ( const ordered& that ) const { return cmp(that) != 0; }

        bool operator> ( const ordered& that ) const { return cmp(that) > 0; }

        bool operator>= ( const ordered& that ) const { return cmp(that) >= 0; }
};

class printable : public virtual object {
public:
        virtual void print(std::ostream&) const = 0;
};

class boolean : public ordered, public printable {
        bool x;

public:
        boolean() = default;

        boolean(bool x) : x(x) {}

        std::unique_ptr<object> new_inst() const override { return std::make_unique<boolean>(); }
        
        std::unique_ptr<object> new_copy() const override { return std::make_unique<boolean>(*this); }

        boolean& operator= (const boolean& that) {
                x = that.x;
                return *this;   
        }

        object& operator= (const object& that) override { return *this = that.as<boolean>(); } /***/

        ~boolean() override = default;

        int cmp(const boolean& that) const { return x == that.x ? 0 : x == false ? -1 : 1; }

        int cmp(const ordered& that) const override { return cmp( that.as<boolean>() ); } /***/

        void print(std::ostream& out) const override { out << (x ? "true" : "false"); }
};

class character : public ordered, public printable {
        char x;

public:
        character() = default;

        character(char x) : x(x) {}

        std::unique_ptr<object> new_inst() const override { return std::make_unique<character>(); }
        
        std::unique_ptr<object> new_copy() const override { return std::make_unique<character>(*this); }

        character& operator= (const character& that) {
                x = that.x;
                return *this;   
        }

        object& operator= (const object& that) override { return *this = that.as<character>(); } /***/

        ~character() override = default;

        int cmp(const character& that) const { return x == that.x ? 0 : x < that.x ? -1 : 1; }

        int cmp(const ordered& that) const override { return cmp( that.as<character>() ); } /***/

        void print(std::ostream& out) const override {
                if ( 0x20 <= x && x <= 0x7E ) { out << "'" << x << "'"; }
                else { out << "'\\" << std::hex << (unsigned int)x << std::setbase(0) << "'"; }
        }
};

class integer : public ordered, public printable {
        int x;

public:
        integer() = default;

        integer(int x) : x(x) {}

        std::unique_ptr<object> new_inst() const override { return std::make_unique<integer>(); }
        
        std::unique_ptr<object> new_copy() const override { return std::make_unique<integer>(*this); }

        integer& operator= (const integer& that) {
                x = that.x;
                return *this;   
        }

        object& operator= (const object& that) override { return *this = that.as<integer>(); } /***/

        ~integer() override = default;

        int cmp(const integer& that) const { return x == that.x ? 0 : x < that.x ? -1 : 1; }

        int cmp(const ordered& that) const override { return cmp( that.as<integer>() ); } /***/

        void print(std::ostream& out) const override { out << x; }
};

class c_string : public printable {
        static constexpr const char* empty = "";
        const char* s;
public:
        c_string() : s(empty) {}

        c_string(const char* s) : s(s) {}

        std::unique_ptr<object> new_inst() const override { return std::make_unique<c_string>(); }

        std::unique_ptr<object> new_copy() const override { return std::make_unique<c_string>(s); }

        c_string& operator= (const c_string& that) {
                s = that.s;
                return *this;
        }

        object& operator= (const object& that) override { return *this = that.as<c_string>(); } /***/

        ~c_string() override = default;

        void print(std::ostream& out) const override { out << s; }
};

class pair : public ordered, public printable {
        std::unique_ptr<object> x;
        std::unique_ptr<object> y;

public:
        pair() = default;

        pair(std::unique_ptr<object>&& x, std::unique_ptr<object>&& y)
                : x(std::move(x)), y(std::move(y)) {}
        
        std::unique_ptr<object> new_inst() const override { return std::make_unique<pair>(); }

        std::unique_ptr<object> new_copy() const override {
                return std::make_unique<pair>(x->new_copy(), y->new_copy());
        }

        pair& operator= (const pair& that) {
                x = that.x->new_copy();
                y = that.y->new_copy();
                return *this;
        }

        object& operator= (const object& that) override { return *this = that.as<pair>(); } /***/

        ~pair() override = default;

        int cmp(const pair& that) const {
                int c = x->as<ordered>().cmp( that.x->as<ordered>() ); /***/
                if ( c != 0 ) return c;
                return y->as<ordered>().cmp( that.y->as<ordered>() ); /***/
        }

        int cmp(const ordered& that) const override { return cmp( that.as<pair>() ); }

        void print(std::ostream& out) const override {
                out << "[";
                x->as<printable>().print(out); /***/
                out << ", ";
                y->as<printable>().print(out); /***/
                out << "]";
        }
};