提升使用功能齐撰写规则 [英] Boost Qi Composing rules using Functions
问题描述
我试图定义为以最小的code重复语言的多个子集部分的boost ::精神::气分析器。要做到这一点，我创建了一些基本规则建设职能。原来的解析器工作正常，但一旦我开始使用排版功能，我的解析器似乎不再工作。
I'm trying to define some Boost::spirit::qi parsers for multiple subsets of a language with minimal code duplication. To do this, I created a few basic rule building functions. The original parser works fine, but once I started to use the composing functions, my parsers no longer seem to work.
一般语言的形式是：
A B: C
有语言的子集，其中 A ， B 或 C 必须是具体的类型，如 A 是一个int，而 B 和 C 是浮动。下面是我用该子语言解析器：
There are subsets of the language where A, B, or C must be specific types, such as A is an int while B and C are floats. Here is the parser I used for that sub language:
using entry = boost::tuple<int, float, float>;
template <typename Iterator>
struct sublang : grammar<Iterator, entry(), ascii::space_type>
{
sublang() : sublang::base_type(start)
{
start = int_ >> float_ >> ':' >> float_;
}
rule<Iterator, entry(), ascii::space_type> start;
};
不过，因为有许多子集，我试图创建建立我的语法规则的函数：
But since there are many subsets, I tried to create a function to build my parser rules:
template<typename AttrName, typename Value>
auto attribute(AttrName attrName, Value value)
{
return attrName >> ':' >> value;
}
所以，我可以为每个子集更轻松地构建解析器不重复信息：
So that I could build parsers for each subset more easily without duplicate information:
// in sublang
start = int_ >> attribute(float_, float_);
然而，这失败，我不知道为什么。在我的测试铿锵，解析只是失败。在G ++，它似乎是程序崩溃。
This fails however and I'm not sure why. In my clang testing, parsing just fails. In g++, it seems the program crashes.
下面是完整的例子code： http://coliru.stacked-crooked.com / A / 8636f19b2e9bff8d
Here's the full example code: http://coliru.stacked-crooked.com/a/8636f19b2e9bff8d
什么是错的当前code和会是什么这个问题的正确的做法？我想避免指定每个子语言解析器的属性和其他元素的语法。
What is wrong with the current code and what would be the correct approach for this problem? I would like to avoid specifying the grammar of attributes and other elements in each sublanguage parser.
推荐答案
很简单：使用汽车与精神（或任何EDSL基于升压原和Boost凤凰城）是最有可能的未定义Behaviour¹
Quite simply: using auto with Spirit (or any EDSL based on Boost Proto and Boost Phoenix) is most likely Undefined Behaviour¹
现在，您可以使用通常解决这个问题。
Now, you can usually fix this using
- BOOST_SPIRIT_AUTO
-
的boost ::原:: DEEP_COPY - 是在最新版的Boost（TODO添加链接） 即将到来的新工厂
- BOOST_SPIRIT_AUTO
boost::proto::deep_copy- the new facility that's coming in the most recent version of Boost (TODO add link)
在这种情况下，
template<typename AttrName, typename Value>
auto attribute(AttrName attrName, Value value) {
return boost::proto::deep_copy(attrName >> ':' >> value);
}
修复它： <大骨节病> 住在Coliru
-
您可以使用
气懒:: []与继承的属性。
我在 prop_key 规则非常类似的事情在<一href=\"http://stackoverflow.com/questions/27746109/reading-json-file-with-c-and-boost/27760376#27760376\">Reading JSON文件，C ++和Boost 。
I do very similar things in the prop_key rule in Reading JSON file with C++ and BOOST.
你可以看看在 <一个href=\"http://www.boost.org/doc/libs/1_57_0/libs/spirit/repository/doc/html/spirit_repository/qi_components/operators/keyword_list.html\"相对=nofollow>关键字列表操作 从精神资源库。它的设计允许像语法更容易建设：
you could have a look at the Keyword List Operator from the Spirit Repository. It's designed to allow easier construction of grammars like:
no_constraint_person_rule %=
kwd("name")['=' > parse_string ]
/ kwd("age") ['=' > int_]
/ kwd("size") ['=' > double_ > 'm']
;
这你可能用 Nabialek把戏结合。我搜索的SO为例子的答案。 （一个是语法平衡问题）
This you could potentially combine with the Nabialek Trick. I'd search the answers on SO for examples. (One is Grammar balancing issue)
¹除了完全无国籍者（<一个href=\"http://stackoverflow.com/questions/10144948/static-functions-from-boost-lambda-or-boost-phoenix/12326204#12326204\">Eric Niebler这个）和前pression占位符。例如参见
¹ Except for entirely stateless actors (Eric Niebler on this) and expression placeholders. See e.g.
- Assigning parsers to auto variables
- undefined behaviour somewhere in boost::spirit::qi::phrase_parse
- C++ Boost qi recursive rule construction
- boost spirit V2 qi bug associated with optimization level
一些例子
- Define在升压精神与子解析器参数解析器
- Generating从另一种解析器前pressions 一个可变参数列表精神解析器前pressions
- Define parsers parameterized with sub-parsers in Boost Spirit
- Generating Spirit parser expressions from a variadic list of alternative parser expressions
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