#include "alga/monoid.hpp"
#pragma once #include"maybe.hpp" template<typename T,typename F> struct monoid{ using M=monoid<T,F>; maybe<T> val; F op; monoid(F op):val(maybe<T>()),op(op){} monoid(T val,F op):val(maybe<T>(val)),op(op){} maybe<T> get(){return val;} void set(T x){return val=maybe<T>(x);} M operator+(const M& rhs){ if(val.is_none())return rhs; if(rhs.val.is_none())return *this; return monoid(op(get().unwrap(),rhs.get().unwrap()),op); } };
#line 2 "alga/maybe.hpp" #include<cassert> /** * @brief Maybe * @see https://ja.wikipedia.org/wiki/%E3%83%A2%E3%83%8A%E3%83%89_(%E3%83%97%E3%83%AD%E3%82%B0%E3%83%A9%E3%83%9F%E3%83%B3%E3%82%B0)#Maybe%E3%83%A2%E3%83%8A%E3%83%89 */ template<typename T> struct maybe{ bool _is_none; T val; maybe():_is_none(true){} maybe(T val):_is_none(false),val(val){} T unwrap()const{ assert(!_is_none); return val; } T unwrap_or(T e)const{ return _is_none?e:val; } bool is_none()const{return _is_none;} bool is_some()const{return !_is_none;} }; template<typename T,typename F> auto expand(F op){ return [&op](const maybe<T>& s,const maybe<T>& t){ if(s.is_none())return t; if(t.is_none())return s; return maybe<T>(op(s.unwrap(),t.unwrap())); }; } #line 3 "alga/monoid.hpp" template<typename T,typename F> struct monoid{ using M=monoid<T,F>; maybe<T> val; F op; monoid(F op):val(maybe<T>()),op(op){} monoid(T val,F op):val(maybe<T>(val)),op(op){} maybe<T> get(){return val;} void set(T x){return val=maybe<T>(x);} M operator+(const M& rhs){ if(val.is_none())return rhs; if(rhs.val.is_none())return *this; return monoid(op(get().unwrap(),rhs.get().unwrap()),op); } };