我如何使用ASCII队长::空间不跳过停产？ [英] How can I use the skipper ascii::space WITHOUT skipping eol?

问题描述

我要使用的boost ::精神解析，我想用phrase_parse功能：

I have to use boost::spirit for parsing, and I want use phrase_parse function :

qi::phrase_parse(str.begin(), str.end(), grammar, ascii::space - qi::eol); 

但第四项（ASCII ::空间 - 齐:: EOL），我的心不是编译器允许。
我如何使用ASCII队长::空间不跳过EOL？

But the fourth term (ascii::space - qi::eol), isnt allowed by my compiler. How can I use the skipper ascii::space WITHOUT skipping eol ?

推荐答案

最简单的答案是

qi::phrase_parse(str.begin(), str.end(), grammar, ascii::blank); 

当然，这取决于你的语法太：如果希望您可能需要更改特定的船长类。 请参阅下面的的通用的方式来处理（虽然你可以只指定齐:: blank_type 的语法是应该只接受齐::空白）。

Of course, it depends on your grammar too: if it expects a specific skipper class you might need to change that. See below for a generic way to handle that (although you could just specify qi::blank_type for a Grammar that should only accept qi::blank).

样品处理任意船长了。

The sample handles arbitrary skippers too.

精神都有影响使用船长的几个指令：

Spirit has several directives that influence the use of skippers:

• <一个href=\"http://www.boost.org/doc/libs/1_48_0/libs/spirit/doc/html/spirit/qi/reference/directive/lexeme.html\"><$c$c>qi::lexeme

将解析子前pression无论船长（在文法例如字符串有用）

will parse the sub-expression regardless of skipper (useful for e.g. string literals in a grammar)

<一个href=\"http://www.boost.org/doc/libs/1_48_0/libs/spirit/doc/html/spirit/qi/reference/directive/raw.html\"><$c$c>qi::raw

将返回原始源迭代范围，即跳过的输入将被包括在结果的意思

will return the raw source iterator range, meaning that skipped input will be included in the result

<一个href=\"http://www.boost.org/doc/libs/1_48_0/libs/spirit/doc/html/spirit/qi/reference/directive/no_skip.html\"><$c$c>qi::no_skip, <一href=\"http://www.boost.org/doc/libs/1_48_0/libs/spirit/doc/html/spirit/qi/reference/directive/skip.html\"><$c$c>qi::skip

可以用来明确地更改用于SUBEX pression队长的类型

can be used to explicitely change the type of skipper used for the subexpression

升压灵网站有关于这样的事情一个很好的文章

The Boost Spirit site has a nice article about things like this

• 解析船长和跳解析器

• Parsing Skippers and Skipping Parsers

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

namespace qi = boost::spirit::qi;

template <typename It, typename Skipper>
    struct parser : qi::grammar<It, Skipper>
{
    parser() : parser::base_type(start)
    {
        start = *qi::int_;
    }

  private:
    qi::rule<It, Skipper> start;
};

template <typename C, typename Skipper>
    void doParse(const C& input, const Skipper& skipper)
{
    auto f(std::begin(input)), l(std::end(input));

    parser<decltype(f), Skipper> p;
    bool ok = qi::phrase_parse(f,l,p,skipper);

    if (ok)   
        std::cout << "parse success\n";
}

int main()
{
    const std::string input = "1 2 3 4";
    doParse(input, qi::blank);
    doParse(input, qi::space);
    doParse(input, ~qi::char_("0-9"));
}

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