value.hpp

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#ifndef value_hpp
#define value_hpp
#include <iomanip>
#include <iostream>
#include <sstream>
#include <utility>
#include <algorithm>
#include <map>
#include <limits>
#include <vector>
#include <tuple>
#include <initializer_list>
#include <functional>

#include "log.hpp"

namespace fv{

namespace detail {
    template<typename T, int N, bool Done, typename... TYPES>
    struct _HomoTuple {
        typedef _HomoTuple<T, N, sizeof...(TYPES)+1==N, TYPES..., T> stype;
        typedef typename stype::type type;
    };

    template<typename T, int N, typename... TYPES>
    struct _HomoTuple<T, N, true, TYPES...> {
        typedef std::tuple<TYPES...> type;
    };
}

template<typename T, int N>
struct HomoTuple {
    typedef detail::_HomoTuple<T, N, N==0> stype;
    typedef typename stype::type type;
};

namespace detail {
    // Convert array into a tuple
    template<typename Array, std::size_t... I>
    decltype(auto) a2t_impl(const Array& a, std::index_sequence<I...>){
        return std::make_tuple(a[I]...);
    }
}

template<typename T, std::size_t N, typename Indices = std::make_index_sequence<N>>
decltype(auto) a2t(const std::array<T, N>& a){
    return detail::a2t_impl(a, Indices());
}

namespace detail {
    template <class F, class Tuple, std::size_t... I>
    constexpr decltype(auto) call_impl(F &&f, Tuple &&t, std::index_sequence<I...>){
        return std::invoke(std::forward<F>(f), std::get<I>(std::forward<Tuple>(t))...);
    }
}

template <class F, class Tuple>
constexpr decltype(auto) call(F &&f, Tuple &&t){
    return detail::call_impl(
        std::forward<F>(f), std::forward<Tuple>(t),
        std::make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>{});
}

namespace detail{
    template <typename T, int N, int I>
    struct t2s_impl{
        public:
            static std::string cvt(typename HomoTuple<T,N>::type& tup, std::function<std::string(T)>& f){
                std::stringstream ss;
                ss << f(std::get<N-I>(tup)) << ", " << t2s_impl<T, N, I+1>::cvt(tup, f);
                return ss.str();
            }
    };

    template <typename T, int N>
    struct t2s_impl<T, N, 0>{
        public:
            static std::string cvt(typename HomoTuple<T,N>::type&, std::function<std::string(T)>&){
                return "";
            }
    };
}

template <typename T, int N>
std::string t2s(typename HomoTuple<T,N>::type& tup, std::function<std::string(T)>& f){
    return detail::t2s_impl<T, N, N>(tup, f);
}

template<typename> class Function; // undefined

class GenFunction {
    private:
        std::string name;
        std::string impl;
    protected:
        inline static bool in_register_function=false;

    public:
        inline static std::map<const std::string, GenFunction*> function_registry;

        GenFunction(const std::string& name, const std::string& impl)
          :name(name),
           impl(impl){ }

        virtual ~GenFunction() { };

        std::string& get_name(){
            return name;
        }

        std::string& get_impl(){
            return impl;
        }

        static std::string format_code(const std::string& code){
            std::stringstream code_out("");
            std::string command("echo \""+code+"\" | clang-format");
            char buffer[255];
            FILE *stream = popen(command.c_str(), "r");
            while (fgets(buffer, 255, stream) != NULL)
                code_out << buffer;
            if (pclose(stream) == 0)
                return code_out.str();
            else
                return code;
        }

        static std::string summary(){
            std::stringstream ss;
            ss << "The following functions have been registered" << std::endl;
            for(auto p : function_registry){
                if (p.second == nullptr) continue;
                ss << "FUNCTION::" << p.second->name  << "@" << p.second << std::endl;
                ss << format_code(p.second->impl);
            }
            return ss.str();
        }

        template <typename T>
        static Function<T>& register_function(const std::string& name, std::function<T> f, const std::string& impl){
            in_register_function = true;
            Function<T>* func;
            if (GenFunction::function_registry[name] != nullptr){
                func = dynamic_cast<Function<T>*>(GenFunction::function_registry[name]);
                if (func == nullptr){
                    ERROR("Trying to register function which has already been registered with a different type");
                }
            } else {
                func = new Function<T>(name, impl, f);
                GenFunction::function_registry[name] = func;
            }
            in_register_function = false;
            return *func;
        }

        template <typename T>
        static Function<T>& lookup_function(const std::string& name){
            if (GenFunction::function_registry[name] == nullptr){
                CRITICAL("Function \"" << name << "\" not previously registered", -1);
            } else {
                Function<T>* func = dynamic_cast<Function<T>*>(GenFunction::function_registry[name]);
                if (func == nullptr){
                    CRITICAL("Function \"" << name << "\" request and register have mismatched types", -1);
                }
                return *GenFunction::function_registry[name];
            }
        }
};


template <typename R, typename... ArgTypes>
class Function<R(ArgTypes...)> : public GenFunction {
    private:
        std::function<R(ArgTypes...)> f;

    public:
        Function(const std::string& name, const std::string& impl, std::function<R(ArgTypes...)> f)
          :GenFunction(name, impl), f(f){
            if (!in_register_function) {
                WARNING("Don't instantiate Function objects directly! Use GenFunction::register_function instead.");
            }
          }
        Function(const std::string& name, std::function<R(ArgTypes...)> f)
          :Function(name, "N/A", f){ }
        ~Function() { }

        R operator()(ArgTypes ...args){
            return f(args...);
        }

};


#define FUNC(f) f, #f

class GenValue;
typedef std::map<std::string, GenValue*> ValueSet;
class GenValue{
    private:
        std::string name;

    protected:
        bool value_valid;
        void _reset(){
            /* if (this->logging_enabled){ */
            /*     std::cout <<  "Resetting validity for " << this->get_name() << std::endl; */
            /* } */
            /* std::cout <<  "Resetting validity for " << this->get_name() << std::endl; */
            this->value_valid = false;
        }
        inline static std::map<const std::string, GenValue*> values;
        inline static std::map<const std::string, GenValue*> aliases;

        bool logging_enabled;

    public:
        GenValue(const std::string& name, const std::string& alias)
          :name(name),
           value_valid(false),
           logging_enabled(false){
            INFO("Registered value: \"" << name << "\" with alias: \"" << alias << "\"");
            values[name] = this;
            if (alias != "")
                GenValue::alias(alias, this);
        }

        const std::string& get_name(){
            return name;
        }

        void set_name(const std::string& new_name){
            values[name] = nullptr;
            name = new_name;
            values[name] = this;
        }

        virtual void log() = 0;

        static void reset(){
            for (auto val : values){
                if (val.second != nullptr){
                    val.second->_reset();
                }
            }
        }

        static GenValue* get_value(const std::string& name){
            if (aliases[name] != nullptr)
                return aliases[name];
            else if (values[name] != nullptr)
                return values[name];
            else{
                ERROR("Could not find alias or value \"" << name << "\". I'll tell you the ones I know about." << std::endl
                        << summary());
                CRITICAL("Aborting... :(",-1);
            }
        }

        static void alias(const std::string& name, GenValue* value){
            if (aliases[name] != nullptr){
                WARNING("WARNING: alias \"" << name << "\" overrides previous entry.");
            }
            aliases[name] = value;
        }

        static GenValue* alias(const std::string& name){
            if (values[name] != nullptr){
                WARNING("Alias \"" << name << "\" does not exist.");
            }
            return aliases[name];
        }

        static std::string summary(){
            std::stringstream ss;
            ss << "The following values have been created:" << std::endl;
            for (auto value : values){
                if (value.second == nullptr) continue;
                ss << "\tVALUE::\"" << value.first << "\" at address " << value.second << std::endl;
            }
            ss << "And these aliases:" << std::endl;
            for (auto alias : aliases){
                std::string orig("VOID");
                if (alias.second == nullptr) continue;
                for (auto value : values){
                    if (alias.second == value.second){
                        orig = value.second->get_name();
                        break;
                    }
                }
                ss << "\tALIAS::\"" << alias.first << "\" referring to \"" << orig << "\"" << std::endl;
            }
            return ss.str();
        }
        friend std::ostream& operator<<(std::ostream& os, const GenValue& gv);
};
std::ostream& operator<<(std::ostream& os, GenValue& gv){
    os << gv.get_name();
    return os;
}


template <typename T>
class Value : public GenValue{
    protected:
        std::function<std::string(T)> value_to_string;

    public:
        Value(const std::string& name, const std::string& alias="")
          :value_to_string([](T){return "";}),
           GenValue(name, alias){ }
        virtual T& get_value() = 0;

        void enable_logging(const std::function<std::string(T)>& value_to_string = [](T){return "";}){
            logging_enabled = true;
            this->value_to_string = value_to_string;
        }

        void disable_logging(){
            logging_enabled = false;
        }
};


template <typename T>
class ObservedValue : public Value<T>{
    private:
        T *val_ref;

    public:
        ObservedValue(const std::string& name, T* val_ref, const std::string& alias="")
          :Value<T>(name, alias),
           val_ref(val_ref){ }

        void log(){
            if(this->logging_enabled){
                INFO(this->get_name() << ": " << this->value_to_string(*val_ref));
            }
        }

        T& get_value(){
            if (!this->value_valid){
                this->value_valid = true;
                this->log();
            }
            return *val_ref;
        }
};


template <typename T>
class DerivedValue : public Value<T>{
    protected:
        T value;

        virtual void update_value() = 0;
    public:
        DerivedValue(const std::string& name, const std::string& alias="")
          :Value<T>(name, alias){ }

        void log(){
            if(this->logging_enabled){
                INFO(this->get_name() << ": " << this->value_to_string(value));
            }
        }

        T& get_value(){
            /* if (this->logging_enabled){ */
            /*     std::cout <<  "Getting value for " << this->get_name() << std::endl; */
            /* } */
            if (!this->value_valid){
                /* if (this->logging_enabled){ */
                /*     std::cout <<  "Updating value for " << this->get_name() << std::endl; */
                /* } */
                update_value();
                this->value_valid = true;
                this->log();
            }
            return value;
        }
};


template <typename T>
class WrapperVector : public DerivedValue<std::vector<T> >{
    private:
        Value<int>* size;
        Value<T*>* data;

        void update_value(){
            int n = size->get_value();
            T* data_ref = data->get_value();
            this->value.assign(data_ref, data_ref+n);
        }

    public:
        WrapperVector(Value<int>* size, Value<T*>* data, const std::string& alias="")
          :DerivedValue<std::vector<T> >("vectorOf("+size->get_name()+","+data->get_name()+")", alias),
           size(size), data(data){ }
};

template <typename T1, typename T2>
class Pair : public DerivedValue<std::pair<T1, T2> >{
    protected:
        std::pair<Value<T1>*, Value<T2>* > value_pair;
        void update_value(){
            this->value.first = value_pair.first->get_value();
            this->value.second = value_pair.second->get_value();
        }

    public:
        Pair(Value<T1> *value1, Value<T2> *value2, const std::string alias="")
          :DerivedValue<std::pair<T1, T2> >("pair("+value1->get_name()+","+value2->get_name()+")", alias),
           value_pair(value1, value2){ }
};

template<typename... T> class _Zip;
template<>
class _Zip<> {
    protected:

        int _get_size(){
            return std::numeric_limits<int>::max();
        }

        std::tuple<> _get_at(int){
            return std::make_tuple();
        }

        std::string _get_name(){
            return "";
        }

    public:
        _Zip() { }
};

template<typename Head, typename... Tail>
class _Zip<Head, Tail...> : private _Zip<Tail...> {
    protected:
        Value<std::vector<Head>>* head;

        int _get_size(){
            int this_size = head->get_value().size();
            int rest_size = _Zip<Tail...>::_get_size();
            return std::min(this_size, rest_size);
        }

        typename std::tuple<Head,Tail...> _get_at(int idx){
            auto tail_tuple = _Zip<Tail...>::_get_at(idx);
            return std::tuple_cat(std::make_tuple(head->get_value()[idx]),tail_tuple);
        }

        std::string _get_name(){
            return head->get_name()+","+_Zip<Tail...>::_get_name();
        }

    public:
        _Zip() { }

        _Zip(Value<std::vector<Head>>* head, Value<std::vector<Tail>>*... tail)
          : _Zip<Tail...>(tail...),
            head(head) { }
};

template <typename... ArgTypes>
class Zip : public DerivedValue<std::vector<std::tuple<ArgTypes...>>>,
             private _Zip<ArgTypes...>{
    protected:
        void update_value(){
            this->value.clear();
            int size = _Zip<ArgTypes...>::_get_size();
            for(int i=0; i<size; i++){
                this->value.push_back(_Zip<ArgTypes...>::_get_at(i));
            }
        }

        std::string _get_name(){
            return "zip("+_Zip<ArgTypes...>::_get_name()+")";
        }

    public:
        Zip(Value<std::vector<ArgTypes>>*... args, const std::string& alias)
          :DerivedValue<std::vector<std::tuple<ArgTypes...>>>("", alias),
           _Zip<ArgTypes...>(args...) {
            this->set_name(_get_name());
        }
};

template<typename> class Map; // undefined
template <typename Ret, typename... ArgTypes>
class Map<Ret(ArgTypes...)> : public DerivedValue<std::vector<Ret>>{
    private:
        typedef Value<std::vector<std::tuple<ArgTypes...>>> arg_type;
        Function<Ret(ArgTypes...)>& fn;
        arg_type* arg;

        void update_value(){
            this->value.clear();
            for(auto tup : arg->get_value()){
                this->value.push_back(call(fn,tup));
            }
        }

    public:
        Map(Function<Ret(ArgTypes...)>& fn, arg_type* arg, const std::string& alias)
          :DerivedValue<std::vector<Ret>>("map("+fn.get_name()+":"+arg->get_name()+")", alias),
           fn(fn), arg(arg){ }

};

template<typename... T> class _Tuple;
template<>
class _Tuple<> {
    protected:

        std::tuple<> _get_value(){
            return std::make_tuple();
        }

        std::string _get_name(){
            return "";
        }

    public:
        _Tuple() { }
};

template<typename Head, typename... Tail>
class _Tuple<Head, Tail...> : private _Tuple<Tail...> {
    protected:
        Value<Head>* head;

        typename std::tuple<Head,Tail...> _get_value(){
            auto tail_tuple = _Tuple<Tail...>::_get_value();
            return std::tuple_cat(std::make_tuple(head->get_value()),tail_tuple);
        }


        std::string _get_name(){
            return head->get_name()+","+_Tuple<Tail...>::_get_name();
        }

    public:
        _Tuple() { }

        _Tuple(Value<Head>* head, Value<Tail>*... tail)
          : _Tuple<Tail...>(tail...),
            head(head) { }
};

template <typename... ArgTypes>
class Tuple : public DerivedValue<std::tuple<ArgTypes...>>,
              private _Tuple<ArgTypes...>{
    protected:
        void update_value(){
            this->value = _Tuple<ArgTypes...>::_get_value();
        }

        std::string _get_name(){
            return "tuple("+_Tuple<ArgTypes...>::_get_name()+")";
        }

    public:
        Tuple(Value<ArgTypes>*... args, const std::string& alias)
          :DerivedValue<std::tuple<ArgTypes...>>("", alias),
           _Tuple<ArgTypes...>(args...) {
            this->set_name(_get_name());
        }
};

template <size_t N, typename... ArgTypes>
class DeTup : public DerivedValue<typename std::tuple_element<N, std::tuple<ArgTypes...>>::type>{
    Value<std::tuple<ArgTypes...>> tup;
    protected:
        void update_value(){
            this->value = std::get<N>(tup->get_value());
        }

    public:
        DeTup(Value<std::tuple<ArgTypes...>>* tup, const std::string& alias)
          :DerivedValue<typename std::tuple_element<N, std::tuple<ArgTypes...>>::type>("detup("+tup->get_name()+")", alias),
           tup(tup) { }
};

template <size_t N, typename... ArgTypes>
class DeTupVector : public DerivedValue<std::vector<typename std::tuple_element<N, std::tuple<ArgTypes...>>::type>>{
    Value<std::vector<std::tuple<ArgTypes...>>>* tup;
    protected:
        void update_value(){
            this->value.clear();
            for( auto& t : tup->get_value()){
                this->value.push_back(std::get<N>(t));
            }
        }

    public:
        DeTupVector(Value<std::vector<std::tuple<ArgTypes...>>>* tup, const std::string& alias)
          :DerivedValue<std::vector<typename std::tuple_element<N, std::tuple<ArgTypes...>>::type>>("detup("+tup->get_name()+")", alias),
           tup(tup) { }
};

template<typename> class Apply; // undefined
template <typename Ret, typename... ArgTypes>
class Apply<Ret(ArgTypes...)> : public DerivedValue<Ret>{
    private:
        Function<Ret(ArgTypes...)>& fn;
        Value<std::tuple<ArgTypes...>>* arg;

        void update_value(){
            auto &tup = arg->get_value();
            this->value = call(fn, tup);
        }

    public:
        Apply(Function<Ret(ArgTypes...)>& fn, Value<std::tuple<ArgTypes...>>* arg, const std::string& alias)
          :DerivedValue<Ret>("apply("+fn.get_name()+":"+arg->get_name()+")", alias),
           fn(fn), arg(arg){ }

};

template<typename T>
class Count : public DerivedValue<int>{
    private:
        Function<bool(T)>& selector;
        Value<std::vector<T> >* v;

        void update_value(){
            value = 0;
            for(auto val : v->get_value()){
                if(selector(val))
                    value++;
            }
        }

    public:
        Count(Function<bool(T)>& selector, Value<std::vector<T>>* v, const std::string alias)
          :DerivedValue<int>("count("+selector.get_name()+":"+v->get_name()+")", alias),
           selector(selector), v(v) { }
};

template<typename T>
class Filter : public DerivedValue<std::vector<T>>{
    private:
        Function<bool(T)>& filter;
        Value<std::vector<T> >* v;

        void update_value(){
            this->value.clear();
            for(auto val : v->get_value()){
                if(this->filter(val))
                    this->value.push_back(val);
            }
        }

    public:
        Filter(Function<bool(T)>& filter, Value<std::vector<T>>* v, const std::string alias)
          :DerivedValue<std::vector<T>>("filter("+filter.get_name()+":"+v->get_name()+")", alias),
           filter(filter), v(v) { }
};

template<typename... ArgTypes>
class TupFilter : public DerivedValue<std::vector<std::tuple<ArgTypes...>>>{
    private:
        typedef std::vector<std::tuple<ArgTypes...>> value_type;
        Function<bool(ArgTypes...)>& filter;
        Value<value_type>* arg;

        void update_value(){
            this->value.clear();
            for(auto val : arg->get_value()){
                if(call(filter,val))
                    this->value.push_back(val);
            }
        }

    public:
        TupFilter(Function<bool(ArgTypes...)>& filter, Value<value_type>* arg, const std::string alias)
          :DerivedValue<value_type>("tupfilter("+filter.get_name()+":"+arg->get_name()+")", alias),
           filter(filter), arg(arg) { }
};

template <typename T>
class Reduce : public DerivedValue<T>{
    private:
        Function<T(std::vector<T>)>& reduce;

        void update_value(){
            this->value = reduce(v->get_value());
        }

    protected:
        Value<std::vector<T> >* v;

    public:
        Reduce(Function<T(std::vector<T>)>& reduce, Value<std::vector<T> >* v, const std::string alias)
          :DerivedValue<T>("reduceWith("+reduce.get_name()+":"+v->get_name()+")", alias),
           reduce(reduce), v(v) { }
};

template <typename T>
class Max : public Reduce<T>{
    public:
        Max(Value<std::vector<T>>* v, const std::string alias)
          :Reduce<T>(GenFunction::register_function<T(std::vector<T>)>("max",
                      FUNC(([](std::vector<T> vec){
                          return *std::max_element(vec.begin(), vec.end());}))),
                      v, alias) { }
};

template <typename T>
class Min : public Reduce<T>{
    public:
        Min(Value<std::vector<T>>* v, const std::string alias)
          :Reduce<T>(GenFunction::register_function<T(std::vector<T>)>("min",
                      FUNC(([](std::vector<T> vec){
                         return *std::min_element(vec.begin(), vec.end());}))),
                     v, alias) { }
};

template <typename T>
class Mean : public Reduce<T>{
    public:
        Mean(Value<std::vector<T>>* v, const std::string alias)
          :Reduce<T>(GenFunction::register_function<T(std::vector<T>)>("mean",
                      FUNC(([](std::vector<T> vec){
                        int n = 0; T sum = 0;
                        for (T e : vec){ n++; sum += e; }
                        return n>0 ? sum / n : 0; }))),
                     v, alias) { }
};

template <typename T>
class Range : public Reduce<T>{
    public:
        Range(Value<std::vector<T>>* v, const std::string alias)
          :Reduce<T>(GenFunction::register_function<T(std::vector<T>)>("range",
                      FUNC(([](std::vector<T> vec){
                        auto minmax = std::minmax_element(vec.begin(), vec.end());
                        return (*minmax.second) - (*minmax.first); }))),
                     v, alias) { }
};

template <typename T>
class ElementOf : public Reduce<T>{
    public:
        ElementOf(Value<int>* index, Value<std::vector<T>>* v, const std::string alias)
          :Reduce<T>(GenFunction::register_function<T(std::vector<T>)>("elementOf",
                     FUNC(([index](std::vector<T> vec){return vec[index->get_value()];}))),
                     v, alias) { }
};

template <typename T>
class ReduceIndex : public DerivedValue<std::pair<T, int> >{
    private:
        Function<std::pair<T,int>(std::vector<T>)>& reduce;
        Value<std::vector<T> >* v;

        void update_value(){
            this->value = reduce(v->get_value());
        }

    public:
        ReduceIndex(Function<std::pair<T,int>(std::vector<T>)>& reduce, Value<std::vector<T> >* v, const std::string alias="")
          :DerivedValue<T>("reduceIndexWith("+reduce.get_name()+":"+v->get_name()+")", alias),
           reduce(reduce), v(v) { }
};

template <typename T>
class MaxIndex : public ReduceIndex<T>{
    public:
        MaxIndex(Value<std::vector<T>>* v, const std::string alias="")
          :ReduceIndex<T>(GenFunction::register_function<T(std::vector<T>)>("maxIndex",
                          FUNC(([](std::vector<T> vec){
                               auto elptr = std::max_element(vec.begin(), vec.end());
                               return std::pair<T,int>(*elptr, int(elptr-vec.begin())); }))),
                          v, alias) { }
};

template <typename T>
class MinIndex : public ReduceIndex<T>{
    public:
        MinIndex(Value<std::vector<T>>* v, const std::string alias="")
          :ReduceIndex<T>(GenFunction::register_function<T(std::vector<T>)>("minIndex",
                          FUNC(([](std::vector<T> vec){
                               auto elptr = std::min_element(vec.begin(), vec.end());
                               return std::pair<T,int>(*elptr, int(elptr-vec.begin())); }))),
                          v, alias) { }
};

template <typename T, int Size>
class Combinations : public DerivedValue<std::vector<typename HomoTuple<T,Size>::type>>{
    private:
        Value<std::vector<T>>* val;
        typedef typename HomoTuple<T,Size>::type tuple_type;

        void update_value(){
            auto& v = val->get_value();
            int data_size = v.size();
            this->value.clear();

            std::vector<bool> selector(data_size);
            std::fill(selector.begin(), selector.begin()+std::min({Size,data_size}), true);
            do {
                std::array<T, Size> perm;
                int idx = 0;
                for (int i=0; i<data_size; i++){
                    if (selector[i]){
                        perm[idx] = v[i];
                        idx++;
                        if (idx == Size) break;
                    }
                }
                this->value.push_back(a2t(perm)); 
            } while(std::prev_permutation(selector.begin(), selector.end()));
        }

        static std::string calc_name(Value<std::vector<T>>* val){
            std::stringstream ss;
            ss << "combinations(" << Size << "," << val->get_name() << ")";
            return ss.str();
        }

    public:
        Combinations(Value<std::vector<T>>* val, const std::string alias="")
          :DerivedValue<std::vector<tuple_type>>(calc_name(val), alias),
           val(val) { }

};

template <typename FST, typename SND>
class CartProduct : public DerivedValue<std::vector<std::tuple<FST,SND>>>{
    private:
        Value<std::vector<FST>>* val1;
        Value<std::vector<SND>>* val2;

        void update_value(){
            this->value.clear();
            auto& v1 = val1->get_value();
            auto& v2 = val2->get_value();
            for(int i=0; i<v1.size(); i++){
                for(int j=0; j<v2.size(); j++){
                    this->value.push_back(std::tuple<FST,SND>(v1[i],v2[j]));
                }
            }
        }

        static std::string calc_name(Value<std::vector<FST>>* val1, Value<std::vector<SND>>* val2){
            std::stringstream ss;
            ss << "cartProduct("
               << val1->get_name() << ", " << val2->get_name()
               << ")";
            return ss.str();
        }

    public:
        CartProduct(Value<std::vector<FST>>* val1, Value<std::vector<SND>>* val2, const std::string alias="")
          :DerivedValue<std::vector<std::tuple<FST,SND>>>(calc_name(val1, val2), alias),
           val1(val1),
           val2(val2) { }
};

template <typename T>
class BoundValue : public DerivedValue<T>{
    protected:
        Function<T()>& f;
        void update_value(){
            this->value = f();
        }
    public:
        BoundValue(Function<T()>& f, const std::string alias="")
          :DerivedValue<T>(f.get_name()+"(<bound>)", alias),
           f(f) { }
};

template <typename T>
class PointerValue : public DerivedValue<T*>{
    protected:
        void update_value(){ }

    public:
        PointerValue(const std::string& name, T* ptr, const std::string alias="")
          :DerivedValue<T*>(name, alias){
            this->value = ptr;
        }
};

template <typename T>
class ConstantValue : public DerivedValue<T>{
    protected:
        void update_value(){ }

    public:
        ConstantValue(const std::string& name, T const_value, const std::string alias="")
            :DerivedValue<T>("const::"+name, alias),
             Value<T>::value(const_value) { }
};
}
#endif // value_hpp