parser = "/execute" > (
        (lit("WriteLine") > stringlit)
      | (lit("Write")    >> +(double_ | int_ | stringlit))
      | lit("NewLine")
      | (lit("Shutdown")  > (stringlit > -int_))

// stringlit is just a quoted string:    
stringlit = lexeme[ '"' >> *~char_('"') >> '"' ];

_{^{注意:我决定向您展示如何接受 /execute Write 的任意数量的各种类型的参数。打电话}}

添加语义操作以将其与我们的 echoService 联系起来和 adminService对象，我们得到这个 REPL 引擎来解析和评估一行:

void execute(const std::string& command)
{
    typedef std::string::const_iterator It;
    It f(command.begin()), l(command.end());

    if (!phrase_parse(f,l, "/execute" > (
            (lit("WriteLine")  
                > stringlit  [ bind(&Echo::WriteLine, ref(echoService), _1) ])
          | (lit("Write") >> +(
                  double_    [ bind(&Echo::WriteDbl,  ref(echoService), _1) ]
                | int_       [ bind(&Echo::WriteInt,  ref(echoService), _1) ]
                | stringlit  [ bind(&Echo::WriteStr,  ref(echoService), _1) ]
            ))
          | (lit("NewLine")  [ bind(&Echo::NewLine,   ref(echoService)) ])
          | (lit("Shutdown")  > (stringlit > (int_ | attr(0))) 
                             [ bind(&Admin::Shutdown, ref(adminService), _1, _2) ])
        ), space))
    {
        // handle error, see full code below
    }
}

现在剩下我们要做的就是编写一个主循环:

int main()
{
    std::string command;
    while (std::getline(std::cin, command))
        execute(command);
}

这很简单，不是吗？

完整的工作示例程序

我在 github ¹ 上发布了该程序的完整工作示例:https://gist.github.com/1314900

有

• 添加了完整的错误处理/报告
• 使用输入文件代替 std::cin(便于测试)
• 将帮助您开始这项工作(命名空间，包括)

您所需要的只是 boost 。我用 g++ 4.6.1(无特殊选项)和 Boost 1.47 对此进行了测试。对于以下测试输入 (input.txt):

/execute WriteLine "bogus"
/execute Write     "here comes the answer: "
/execute Write     42
/execute Write     31415e-4
/execute Write     "that is the inverse of" 24 "and answers nothing"
/execute Shutdown  "Bye" 9
/execute Shutdown  "Test default value for retval"

演示程序的输出是

WriteLine('bogus');
Write(string: 'here comes the answer: ');
Write(double: 42);
Write(double: 3.1415);
Write(string: 'that is the inverse of');
Write(double: 24);
Write(string: 'and answers nothing');
Shutdown(reason: 'Bye', retval: 9)
Shutdown(reason: 'Test default value for retval', retval: 0)

• 注意:我注释掉了 exit(...)调用我演示如何制作 retval参数可选，同时提供默认值 ( attr(0) )
• 注意:如何双31415e-4正确打印为 3.1415
• 注意:/execute Write的多个参数如何在对 echoService.Write(...) 的单独调用中得到翻译取决于输入参数的实际类型
• 注意:如何完全忽略行内空格(字符串文字之外)的存在。您可以使用任意数量的制表符/空格

<子> ¹ 为了后代的利益，github 是否应该停止托管我的要点:

#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <fstream>

namespace qi  = boost::spirit::qi;
namespace phx = boost::phoenix;

///////////////////////////////////
// 'domain classes' (scriptables)
struct Echo
{
    void WriteLine(const std::string& s) { std::cout << "WriteLine('"     << s << "');" << std::endl; }
    void WriteStr (const std::string& s) { std::cout << "Write(string: '" << s << "');" << std::endl; }
    void WriteInt (int i)                { std::cout << "Write(int: "     << i <<  ");" << std::endl; }
    void WriteDbl (double d)             { std::cout << "Write(double: "  << d <<  ");" << std::endl; }
    void NewLine  ()                     { std::cout << "NewLine();"                    << std::endl; }
} echoService;

struct Admin
{
    void Shutdown(const std::string& reason, int retval) 
    { 
        std::cout << "Shutdown(reason: '" << reason << "', retval: " << retval << ")" << std::endl;
        // exit(retval);
    }
} adminService;

void execute(const std::string& command)
{
    typedef std::string::const_iterator It;
    It f(command.begin()), l(command.end());

    using namespace qi;
    using phx::bind;
    using phx::ref;

    rule<It, std::string(), space_type> stringlit = lexeme[ '"' >> *~char_('"') >> '"' ];

    try
    {
        if (!phrase_parse(f,l, "/execute" > (
                (lit("WriteLine")  
                    > stringlit  [ bind(&Echo::WriteLine, ref(echoService), _1) ])
              | (lit("Write") >> +(
                      double_    [ bind(&Echo::WriteDbl,  ref(echoService), _1) ] // the order matters
                    | int_       [ bind(&Echo::WriteInt,  ref(echoService), _1) ]
                    | stringlit  [ bind(&Echo::WriteStr,  ref(echoService), _1) ]
                ))
              | (lit("NewLine")  [ bind(&Echo::NewLine,   ref(echoService)) ])
              | (lit("Shutdown")  > (stringlit > (int_ | attr(0))) 
                                 [ bind(&Admin::Shutdown, ref(adminService), _1, _2) ])
            ), space))
        {
            if (f!=l) // allow whitespace only lines
                std::cerr << "** (error interpreting command: " << command << ")" << std::endl;
        }
    }
    catch (const expectation_failure<It>& e)
    {
        std::cerr << "** (unexpected input '" << std::string(e.first, std::min(e.first+10, e.last)) << "') " << std::endl;
    }

    if (f!=l)
        std::cerr << "** (warning: skipping unhandled input '" << std::string(f,l) << "')" << std::endl;
}

int main()
{
    std::ifstream ifs("input.txt");

    std::string command;
    while (std::getline(ifs/*std::cin*/, command))
        execute(command);
}