提升精灵数字解析整数和浮点 [英] boost spirit qi numeric parsing of integer and floating points

问题描述

我想了解以下结果。测试用例代码是

i am trying to make sense of the following result. The test case code is

#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <boost/spirit/include/phoenix_fusion.hpp>
#include <boost/spirit/include/phoenix_stl.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/variant/recursive_variant.hpp>
#include <boost/spirit/home/support/context.hpp>
#include <boost/spirit/home/phoenix.hpp>
#include <boost/foreach.hpp>

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
#include <vector>

namespace sp = boost::spirit;
namespace qi = boost::spirit::qi;
using namespace boost::spirit::ascii;

namespace fusion = boost::fusion;
namespace phoenix = boost::phoenix;

using phoenix::at_c;
using phoenix::push_back;
using phoenix::bind;

template <typename P>
void test_parser(
    char const* input, P const& p, bool full_match = true)
{
    using boost::spirit::qi::parse;

    char const* f(input);
    char const* l(f + strlen(f));
    if (parse(f, l, p) && (!full_match || (f == l)))
        std::cout << "ok" << std::endl;
    else
        std::cout << "fail" << std::endl;
}


int main() {

test_parser("+12345", qi::int_ ); //Ok
test_parser("+12345", qi::double_ - qi::int_ ); //failed, as expected
test_parser("+12345.34", qi::int_ );  // failed, as expected
test_parser("+12345.34", qi::double_ - qi::int_ );  //failed but it should be Ok!
};

这里的动机是我想将数字12345匹配为整数， '12345.34'将匹配double_和never int_，但是倒数情况不是真的; '12345'匹配整数（int_）和浮点（double_）。我试过double_ - int_，它成功失败匹配'12345'。但是我的希望是，最后一个测试用例12345.34将正确匹配double_ - int_，但是我得到的结果是不匹配。

the motivation here is that i want to match numbers '12345' as integers and NEVER as floating points. '12345.34' will match double_ and never int_ but the reciprocal case is not true; '12345' matches both integers (int_ ) and floating point (double_ ). I tried double_ - int_ and it successfully failed to match '12345'. However my hope was that the last test case '12345.34' would positively match double_ - int_, but the result i get is fail to match.

为什么会这样，我如何获得一个只匹配整数和另一个只匹配浮点的解析器（例如在c中，5.0将被解释为浮点）

Why this is so, and how do i get a parser that only matches integers and another that only matches floating points (like in c, 5.0 would be interpreted as floating point)

推荐答案

对于你的具体例子，我认为它实际上描述在 Boost Spirit文档 RealPolicies 专业化。为了使事情更容易一些，我鞭打了一个快速的真正的解析器，只解析实数而不是整数（或至少它与您的简化示例）：

For your specific example, I think it's actually described in the Boost Spirit documentation under RealPolicies Specialization. To make things a bit easier for you, I whipped out a quick "real" parser, that only parses real numbers and not integers(or at least it worked with your simplified examples):

template <typename T>
struct strict_real_policies : qi::real_policies<T>
{
    static bool const expect_dot = true;
};

qi::real_parser< double, strict_real_policies<double> > real;

你可以像任何其他解析器一样使用它您可能需要添加：

And you can use this just like any other parser(like int_ and double_). You might have to add:

#include <boost/spirit/include/qi_numeric.hpp>

要编译。

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