c++ - 如何在 Boost::Statechart 中向一个状态添加超过 20 个转换？

Question

我不得不承认，我对 C++ 和 Boost Statecharts 还是比较陌生。我玩了一下 Statechart 库，想构建一些“更大”的状态机。

我举一个非常简单的例子来说明我的问题。让我们假设一个只有一个状态和很多自转换的状态机。如何构建这样的东西？ gcc(4.5.2) 编译器拒绝超过 20 个转换的所有内容(“错误的模板参数数量(21，应该是 20)”)

下面是一些示例代码:

#include <boost/statechart/event.hpp>
#include <boost/statechart/state_machine.hpp>
#include <boost/statechart/simple_state.hpp>
#include <boost/statechart/transition.hpp>
#include <iostream>
#include <boost/mpl/list.hpp>
namespace sc = boost::statechart;

struct MyEvent1: sc::event<MyEvent1> {};
struct MyEvent2: sc::event<MyEvent2> {};
//...
struct MyEvent21: sc::event<MyEvent21> {};

struct MyState;
struct Statemachine: sc::state_machine<Statemachine, MyState> {};

struct MyState: sc::simple_state<MyState, Statemachine> {
    typedef boost::mpl::list<
            sc::transition< MyEvent1, MyState >  , 
            sc::transition< MyEvent2, MyState > , 
            //...
            sc::transition< MyEvent21 >     
    > reactions;
};

int main() {
    //..
    return 0;
}

Answer 1

您的问题实际上与 Boost.Statechart 无关，而是与您正在使用其类型列表的 Boost.MPL 相关。来自Boost.MPL docs :

BOOST_MPL_LIMIT_LIST_SIZE is an overridable configuration macro regulating the maximum arity of the list's and list_c's variadic forms. In this implementation of the library, BOOST_MPL_LIMIT_LIST_SIZE has a default value of 20.

它继续:

To override the default limit, define BOOST_MPL_LIMIT_LIST_SIZE to the desired maximum arity rounded up to the nearest multiple of ten before including any library header.

所以大概您需要在任何 #include 之前添加以下内容:

#define BOOST_MPL_LIMIT_LIST_SIZE 30