如何将Boost Spirit与超过20种类型的变体一起使用？ [英] How to use Boost Spirit with variant with more than 20 types?

问题描述

我正在使用Boost Spirit解析一个非常复杂的语法，而我遇到的是一个具有20多种类型（此处为21种）的变体的问题：

I'm parsing a quite complex grammar with Boost Spirit and I'm facing a problem with a variant that have more than 20 types (21 here):

namespace eddic { namespace ast {

typedef boost::mpl::vector<
            Integer,
            IntegerSuffix,
            Float,
            Litteral,
            VariableValue,
            DereferenceValue,
            Expression,
            Unary,
            Null,
            True,
            False,
            ArrayValue,
            FunctionCall,
            MemberFunctionCall,
            Cast,
            BuiltinOperator,
            Assignment,
            SuffixOperation,
            PrefixOperation,
            Ternary
        > types_initial;

typedef boost::mpl::push_back<types_initial, New>::type types;
typedef boost::make_variant_over<types>::type Value;

}}

Boost Spirit无法识别最后一种类型（eddic： ：ast :: New）添加了push_back。当我解析具有此元素的内容时，它将失败并显示以下错误：

Boost Spirit does not recognize the last type (eddic::ast::New) added with push_back. When I parse something that have this element, it fails with this error:

eddic：/ usr / include / boost / variant / detail / visitation_impl.hpp：264：
类型名Visitor :: result_type
boost :: detail :: variant :: visitation_impl（int，int，Visitor& ;, VoidPtrCV，
mpl _ :: false_，NoBackupFlag，其中*，step0 *）[其中哪个=
mpl _ :: int_< 0>; step0 =
boost :: detail :: variant :: visitation_impl_step，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl： ：v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item ，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
0>，0>，0>，0>，0>，0>，0>，0> ，0>，0>，0>，0>，0>，0>，0>，0>，0>，
0>，0>，0>，0>，0l>，
boost :: mpl :: v_iter，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
boost :: mpl :: v_item，
提升：: mpl :: v_item，
提升：: mpl :: v_item，
提升：: mpl :: v_item，
提升：: mpl :: v_item，
提升：: mpl :: v_item，
提升：: mpl :: v_item，
提升：: mpl :: v_item，
提升：: mpl： ：v_item，
boost :: mpl :: v_item，
0>，0>，0>，0>，0>，0>，0>，0>，0>，0>，0 >，0>，0>，0>，0>，0>，0>，
0>，0>，0>，0>，21l>>;访客=
boost :: variant，boost :: mpl :: vector，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，eddic :: ast :: Null ，
eddic :: ast :: True，eddic :: ast :: False，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred>，0>>，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_ ，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant： ：void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void _> :: assigner; VoidPtrCV = const void *;
NoBackupFlag =
boost :: variant，boost :: mpl :: vector，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，eddic :: ast :: Null，
eddic :: ast :: True，eddic :: ast :: False，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred，
eddic :: ast :: Deferred>，0>>，
boost :: detail :: variant： ：void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost： ：detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: v oid_，
boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，
boost :: detail :: variant :: void _> :: has_fallback_type_; typename
Visitor :: result_type = void; mpl _ :: false_ = mpl _ :: bool_]：
断言`！ Boost.Variant内部错误：超出范围。'
失败。

eddic: /usr/include/boost/variant/detail/visitation_impl.hpp:264: typename Visitor::result_type boost::detail::variant::visitation_impl(int, int, Visitor&, VoidPtrCV, mpl_::false_, NoBackupFlag, Which*, step0*) [with Which = mpl_::int_<0>; step0 = boost::detail::variant::visitation_impl_step, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0l>, boost::mpl::v_iter, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, boost::mpl::v_item, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 0>, 21l> >; Visitor = boost::variant, boost::mpl::vector, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Null, eddic::ast::True, eddic::ast::False, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred >, 0> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_>::assigner; VoidPtrCV = const void*; NoBackupFlag = boost::variant, boost::mpl::vector, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Null, eddic::ast::True, eddic::ast::False, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred, eddic::ast::Deferred >, 0> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_>::has_fallback_type_; typename Visitor::result_type = void; mpl_::false_ = mpl_::bool_]: Assertion `!"Boost.Variant internal error: 'which' out of range."' failed.

如果我交换两个元素（例如Ternary和New），则New会被正确识别，但Ternary不会被识别。它只是最后一个失败的元素。

If I swap two elements (Ternary and New for example), New is correctly recognized, but not Ternary. It is only the last element that fails.

我已经尝试过使用push_front或vector21，但是它并没有改变任何东西，它始终是有问题的最后一个元素。我认为这是因为Spirit在将变量复制到我的variant_over类型之前在内部使用了一个变量。

I already tried using push_front or vector21, but it doesn't change anything, it's always the last element that have problem. In my opinion it comes from the fact that Spirit uses a variant internally before copying it to my variant_over type.

是否有解决此问题的方法？

Is there a workaround to this problem ?

我可以将数字减少到20，但是问题是，将来我肯定会拥有更多。

I could probably reduce the number to 20, but the problem is that I will certainly have more than that in the future.

非常感谢任何想法

推荐答案

定义 BOOST_MPL_LIMIT_VECTOR_SIZE 达到您想要的任何新限制，但过高通常表示存在设计问题，因此可能值得考虑。

Define BOOST_MPL_LIMIT_VECTOR_SIZE to whatever new limit you want, but going this high is usually a hint at design problems so it might be worth to give it some consideration.

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