變異問題，編譯文件

我試圖從這個頁面編譯如下代碼： http://www.pdc.kth.se/training/Talks/C++/boost/libs/variant/doc/sample.html 變異問題，編譯文件

在「A二叉樹的實現」，我得到一噸，我遇到了有關解決麻煩的錯誤。我使用gcc 3.4.5和codeblocks。

#include <iostream> 

#include "boost/variant.hpp" 
#include "boost/incomplete.hpp" 


using boost::variant; 
using boost::incomplete; 
using std::cout; 
using std::endl; 


struct non_leaf_node; // Forward declaration 

// Define a variant with these two types: 
// 1) int 
// 2) The (incomplete) non_leaf_node struct 
typedef variant<int, incomplete<non_leaf_node> > tree_node; 

struct non_leaf_node 
{ 
    non_leaf_node(const tree_node& l, int num, const tree_node& r) 
     : left_(l), right_(r), num_(num) { } 
    non_leaf_node(const non_leaf_node& other) 
     : left_(other.left_), right_(other.right_), num_(other.num_) { } 

    int num_; 
    tree_node left_; 
    tree_node right_; 
}; 


struct tree_printer : boost::static_visitor<void> 
{ 
    void operator()(int n) const 
    { 
     cout << n << ' '; 
    } 

    void operator()(const non_leaf_node& node) const 
    { 
     boost::apply_visitor(*this, node.left_); 
     cout << node.num_ << ' '; 
     boost::apply_visitor(*this, node.right_); 
    } 
}; 


int main(int, char* []) 
{ 
    //Build a binary search tree: 
    non_leaf_node a(3,4, 6); 
    non_leaf_node b(19, 20, 23); 
    non_leaf_node c(a,10, b); 

    tree_node root(c); 

    //Perform an in-order walk 
    boost::apply_visitor(tree_printer(), root); 

    return 0; 
}

而且回溯編譯期間：

> C:\boostvariantBtree\boostvariantBtree.cpp||In 
> constructor 
> `non_leaf_node::non_leaf_node(const 
> tree_node&, int, const tree_node&)':| 
> C:\boostvariantBtree\boostvariantBtree.cpp|24|warning: 
> `non_leaf_node::right_' will be 
> initialized after| 
> C:\boostvariantBtree\boostvariantBtree.cpp|22|warning: 
> `int non_leaf_node::num_'| 
> C:\boostvariantBtree\boostvariantBtree.cpp|19|warning: 
> when initialized here| 
> C:\boostvariantBtree\boostvariantBtree.cpp|24|warning: 
> `non_leaf_node::right_' will be 
> initialized after| 
> C:\boostvariantBtree\boostvariantBtree.cpp|22|warning: 
> `int non_leaf_node::num_'| 
> C:\boostvariantBtree\boostvariantBtree.cpp|20|warning: 
> when initialized here| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp||In 
> member function `typename 
> Visitor::result_type 
> boost::detail::variant::invoke_visitor<Visitor>::internal_visit(T&, 
> int) [with T = const 
> boost::incomplete<non_leaf_node>, 
> Visitor = const tree_printer]':| 
> C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\detail\visitation_impl.hpp|128|instantiated 
> from `typename Visitor::result_type 
> boost::detail::variant::visitation_impl_invoke_impl(int, 
> Visitor&, VoidPtrCV, T*, mpl_::true_) 
> [with Visitor = 
> boost::detail::variant::invoke_visitor<const 
> tree_printer>, VoidPtrCV = const 
> void*, T = 
> boost::incomplete<non_leaf_node>]'| 
> C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\detail\visitation_impl.hpp|170|instantiated 
> from `typename Visitor::result_type 
> boost::detail::variant::visitation_impl_invoke(int, 
> Visitor&, VoidPtrCV, T*, NoBackupFlag, 
> int) [with Visitor = 
> boost::detail::variant::invoke_visitor<const 
> tree_printer>, VoidPtrCV = const 
> void*, T = 
> boost::incomplete<non_leaf_node>, 
> NoBackupFlag = boost::variant<int, 
> boost::incomplete<non_leaf_node>, 
> boost::detail::variant::void_, 
> boost::detail::variant::void_, 
> boost::detail::variant::void_, 
> boost::detail::variant::void_, 
> boost::detail::variant::void_, boo| 
> C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\detail\visitation_impl.hpp|256|instantiated 
> from `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::l_iter<boost::mpl::l_item<mpl_::long_<2l>, 
> int, 
> boost::mpl::l_item<mpl_::long_<1l>, 
> boost::incomplete<non_leaf_node>, 
> boost::mpl::l_end> > >, 
> boost::mpl::l_iter<boost::mpl::l_end> 
> >, Visitor = boost::detail::variant::invoke_visitor<const 
> tree_printer>, | C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|1771|instantiated 
> from `static typename 
> Visitor::result_type 
> boost::variant<T0, T1, T2, T3, T4, T5, 
> T6, T7, T8, T9, T10, T11, T12, T13, 
> T14, T15, T16, T17, T18, 
> T19>::internal_apply_visitor_impl(int, 
> int, Visitor&, VoidPtrCV) [with 
> Visitor = 
> boost::detail::variant::invoke_visitor<const 
> tree_printer>, VoidPtrCV = const 
> void*, T0_ = int, T1 = 
> boost::incomplete<non_leaf_node>, T2 = 
> boost::detail::variant::void_, T3 = 
> boost::detail::variant::void_, T4 = 
> boost::detail::variant::void_, T5 = 
> boost::detail::variant::vo| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|1796|instantiated 
> from `typename Visitor::result_type 
> boost::variant<T0, T1, T2, T3, T4, T5, 
> T6, T7, T8, T9, T10, T11, T12, T13, 
> T14, T15, T16, T17, T18, 
> T19>::internal_apply_visitor(Visitor&) 
> const [with Visitor = 
> boost::detail::variant::invoke_visitor<const 
> tree_printer>, T0_ = int, T1 = 
> boost::incomplete<non_leaf_node>, T2 = 
> boost::detail::variant::void_, T3 = 
> boost::detail::variant::void_, T4 = 
> boost::detail::variant::void_, T5 = 
> boost::detail::variant::void_, T6 = 
> boost::detail::variant::void_, T7 = 
> boost:| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|1820|instantiated 
> from `typename Visitor::result_type 
> boost::variant<T0, T1, T2, T3, T4, T5, 
> T6, T7, T8, T9, T10, T11, T12, T13, 
> T14, T15, T16, T17, T18, 
> T19>::apply_visitor(Visitor&) const 
> [with Visitor = const tree_printer, 
> T0_ = int, T1 = 
> boost::incomplete<non_leaf_node>, T2 = 
> boost::detail::variant::void_, T3 = 
> boost::detail::variant::void_, T4 = 
> boost::detail::variant::void_, T5 = 
> boost::detail::variant::void_, T6 = 
> boost::detail::variant::void_, T7 = 
> boost::detail::variant::void_, T8 = 
> boost::detail::vari| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\detail\apply_visitor_unary.hpp|76|instantiated 
> from `typename Visitor::result_type 
> boost::apply_visitor(const Visitor&, 
> Visitable&) [with Visitor = 
> tree_printer, Visitable = const 
> tree_node]'| 
> C:\boostvariantBtree\boostvariantBtree.cpp|34|instantiated 
> from here| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|832|error: 
> no match for call to `(const 
> tree_printer) (const 
> boost::incomplete<non_leaf_node>&)'| 
> C:\boostvariantBtree\boostvariantBtree.cpp|29|note: 
> candidates are: void 
> tree_printer::operator()(int) const| 
> C:\boostvariantBtree\boostvariantBtree.cpp|33|note: 
> void tree_printer::operator()(const 
> non_leaf_node&) const| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|832|error: 
> return-statement with a value, in 
> function returning 'void'| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp||In 
> member function `typename 
> Visitor::result_type 
> boost::detail::variant::invoke_visitor<Visitor>::internal_visit(T&, 
> int) [with T = 
> boost::incomplete<non_leaf_node>, 
> Visitor = const tree_printer]':| 
> C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\detail\visitation_impl.hpp|128|instantiated 
> from `typename Visitor::result_type 
> boost::detail::variant::visitation_impl_invoke_impl(int, 
> Visitor&, VoidPtrCV, T*, mpl_::true_) 
> [with Visitor = 
> boost::detail::variant::invoke_visitor<const 
> tree_printer>, VoidPtrCV = void*, T = 
> boost::incomplete<non_leaf_node>]'| 
> C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\detail\visitation_impl.hpp|170|instantiated 
> from `typename Visitor::result_type 
> boost::detail::variant::visitation_impl_invoke(int, 
> Visitor&, VoidPtrCV, T*, NoBackupFlag, 
> int) [with Visitor = 
> boost::detail::variant::invoke_visitor<const 
> tree_printer>, VoidPtrCV = void*, T = 
> boost::incomplete<non_leaf_node>, 
> NoBackupFlag = boost::variant<int, 
> boost::incomplete<non_leaf_node>, 
> boost::detail::variant::void_, 
> boost::detail::variant::void_, 
> boost::detail::variant::void_, 
> boost::detail::variant::void_, 
> boost::detail::variant::void_, 
> boost::de| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\detail\visitation_impl.hpp|256|instantiated 
> from `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::l_iter<boost::mpl::l_item<mpl_::long_<2l>, 
> int, 
> boost::mpl::l_item<mpl_::long_<1l>, 
> boost::incomplete<non_leaf_node>, 
> boost::mpl::l_end> > >, 
> boost::mpl::l_iter<boost::mpl::l_end> 
> >, Visitor = boost::detail::variant::invoke_visitor<const 
> tree_printer>, | C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|1771|instantiated 
> from `static typename 
> Visitor::result_type 
> boost::variant<T0, T1, T2, T3, T4, T5, 
> T6, T7, T8, T9, T10, T11, T12, T13, 
> T14, T15, T16, T17, T18, 
> T19>::internal_apply_visitor_impl(int, 
> int, Visitor&, VoidPtrCV) [with 
> Visitor = 
> boost::detail::variant::invoke_visitor<const 
> tree_printer>, VoidPtrCV = void*, T0_ 
> = int, T1 = boost::incomplete<non_leaf_node>, T2 = 
> boost::detail::variant::void_, T3 = 
> boost::detail::variant::void_, T4 = 
> boost::detail::variant::void_, T5 = 
> boost::detail::variant::void_, T| 
> C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|1785|instantiated 
> from `typename Visitor::result_type 
> boost::variant<T0, T1, T2, T3, T4, T5, 
> T6, T7, T8, T9, T10, T11, T12, T13, 
> T14, T15, T16, T17, T18, 
> T19>::internal_apply_visitor(Visitor&) 
> [with Visitor = 
> boost::detail::variant::invoke_visitor<const 
> tree_printer>, T0_ = int, T1 = 
> boost::incomplete<non_leaf_node>, T2 = 
> boost::detail::variant::void_, T3 = 
> boost::detail::variant::void_, T4 = 
> boost::detail::variant::void_, T5 = 
> boost::detail::variant::void_, T6 = 
> boost::detail::variant::void_, T7 = 
> boost::detai| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|1810|instantiated 
> from `typename Visitor::result_type 
> boost::variant<T0, T1, T2, T3, T4, T5, 
> T6, T7, T8, T9, T10, T11, T12, T13, 
> T14, T15, T16, T17, T18, 
> T19>::apply_visitor(Visitor&) [with 
> Visitor = const tree_printer, T0_ = 
> int, T1 = 
> boost::incomplete<non_leaf_node>, T2 = 
> boost::detail::variant::void_, T3 = 
> boost::detail::variant::void_, T4 = 
> boost::detail::variant::void_, T5 = 
> boost::detail::variant::void_, T6 = 
> boost::detail::variant::void_, T7 = 
> boost::detail::variant::void_, T8 = 
> boost::detail::variant::v| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\detail\apply_visitor_unary.hpp|76|instantiated 
> from `typename Visitor::result_type 
> boost::apply_visitor(const Visitor&, 
> Visitable&) [with Visitor = 
> tree_printer, Visitable = tree_node]'| 
> C:\boostvariantBtree\boostvariantBtree.cpp|49|instantiated 
> from here| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|832|error: 
> no match for call to `(const 
> tree_printer) 
> (boost::incomplete<non_leaf_node>&)'| 
> C:\boostvariantBtree\boostvariantBtree.cpp|29|note: 
> candidates are: void 
> tree_printer::operator()(int) const| 
> C:\boostvariantBtree\boostvariantBtree.cpp|33|note: 
> void tree_printer::operator()(const 
> non_leaf_node&) const| C:\Program 
> Files\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\boost\variant\variant.hpp|832|error: 
> return-statement with a value, in 
> function returning 'void'| ||=== Build 
> finished: 4 errors, 6 warnings ===|

來源

2011-05-17 pandoragami

請不要在標題中寫標籤。 – 2011-05-17 19:43:35

@Tomalak：這是網站的政策，還是私人寵物？ – 2011-05-17 19:47:45

@John：都是，真的。我不認爲它是明確寫在常見問題解答中的（創始人可能認爲它不需要^ _ ^），但是很多人並沒有這麼做，顯然完全是多餘的。 – 2011-05-17 19:58:17

至於我看到，當前boost似乎沒有incomplete.hpp。如果您boost是移除線 #include "boost/incomplete.hpp"和using boost::incomplete;，
和更換線

typedef variant<int, incomplete<non_leaf_node> > tree_node;

與

typedef variant<int, boost::recursive_wrapper<non_leaf_node> > tree_node;

最近，可能的代碼會被編譯。這是對ideone的測試。
如果你需要一個遞歸類型，這個文件 Recursive variant types 可能會有所幫助。

來源

2011-05-17 19:41:44

變異問題，編譯文件

回答

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