如何更改规则的解析器 [英] how to change the parser of a rule

问题描述

是否可以在运行时修改规则的解析器?我能够动态创建解析器(派生自parser_base的类)，但是我不知道如何将新的解析器分配给现有规则.

基本上，我的问题是我想为由数字(如在我的所有解析器输入中不变的意义上称它们为常量)和符号(我想要的变体)这样的元素组成的行定义一个解析器使用动态解析器​​方法捕获).由于这些符号基于运行时的当前环境，因此我认为我需要一个动态解析器​​.

最小的问题，我想要符号和行尾:

namespace parser
{
    x3::rule<class line, ast::line> line = "line";
    auto const line_def = variants_def >> lineend_def;
    BOOST_SPIRIT_DEFINE(line);
}

using line_type = boost::spirit::x3::rule<class client::parser::line, ast::line>;
line_type line(boost::spirit::x3::plus<boost::spirit::x3::symbols_parser<boost::spirit::char_encoding::standard, client::ast::command, boost::spirit::x3::tst<boost::spirit::char_encoding::standard::char_type, client::ast::command>>> symbols_parser)
{
    auto line_end = lineend();
    auto const line_def2 = symbols_parser >> line_end;
    return parser::line; // <-- how can I change the line_type to use line_def2?
}

此代码可能远非最少，但不幸的是，我还不太熟悉C ++.

解决方案

您不能.

实际上，我撒谎了，您可以在动态库中拥有具有相同id的不同解析器，并通过来回切换动态库来更改规则的解析器，但是请不要这样做.

Is it possible to modify the parser of a rule at runtime? I am able to dynamically create parsers (classes that are derived from parser_base), but I dont know how I can assign the new parser to an existing rule.

Basically my problem is that I want to define a parser for a line that consists of elements like numbers (lets call them constants in the sense that they are invariant over all my parser input) and symbols (the variants that I want to capture with a dynamic parser approach). Since the symbols are based on the current environment at runtime I think I need a dynamic parser.

minimalistic issue, I want symbols and a line-end:

namespace parser
{
    x3::rule<class line, ast::line> line = "line";
    auto const line_def = variants_def >> lineend_def;
    BOOST_SPIRIT_DEFINE(line);
}

using line_type = boost::spirit::x3::rule<class client::parser::line, ast::line>;
line_type line(boost::spirit::x3::plus<boost::spirit::x3::symbols_parser<boost::spirit::char_encoding::standard, client::ast::command, boost::spirit::x3::tst<boost::spirit::char_encoding::standard::char_type, client::ast::command>>> symbols_parser)
{
    auto line_end = lineend();
    auto const line_def2 = symbols_parser >> line_end;
    return parser::line; // <-- how can I change the line_type to use line_def2?
}

This code might be far from minimal, but unfortunately Im not so familiar with C++ yet.

解决方案

You cannot.

Actually, I lied, you can have different parsers with the same id in dynamic libraries and change the rule's parser by switching dynamic libraries back and forth, but please, do not do this.

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