2

请考虑以下几点：

// from main file

// first arguement gets enc_array
Rock rock (voice.getEncArray());
// getEncArray() gets a vector of vectors:
// std::vector<std::vector<unsigned int> > enc_array;

// in rock.hpp file, consider members
Rock( const std::vector<std::vector<unsigned int> > &);

std::vector<std::vector<unsigned int> * > remaining;

const std::vector<std::vector<unsigned int> > * population;

// in rock.cpp
Rock::Rock ( const vector<vector<unsigned int> > & v) :
  population (&v),
  ....

// in one of the class member functions
for ( vector<vector<unsigned int> >::const_iterator ci = population->begin(); ci != population->end(); ++ci ) {
    // for some indexes...
    remaining.push_back (& (*ci));      // <------  PROBLEM
}

gcc 报告：

error: no matching function for call to 'std::vector<std::vector<unsigned int>*>::push_back(const std::vector<unsigned int>*)'

note: void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = std::vector<unsigned int>*; _Alloc = std::allocator<std::vector<unsigned int>*>; std::vector<_Tp, _Alloc>::value_type = std::vector<unsigned int>*] <near match>

note:   no known conversion for argument 1 from 'const std::vector<unsigned int>*' to 'std::vector<unsigned int>* const&'

我知道我正在尝试将vector<int>那些被认为const是非 const的地址推送vector。填满后remaining，没有其他方法会改变它的数据，所以实际上应该是const. 但我不能声明remaining为 a const vector，因为它会给出错误。

error: no matching function for call to 'std::vector<std::vector<unsigned int>*>::push_back(const std::vector<unsigned int>*) const'

note: candidate is:
note: void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = std::vector<unsigned int>*; _Alloc = std::allocator<std::vector<unsigned int>*>; std::vector<_Tp, _Alloc>::value_type = std::vector<unsigned int>*] <near match>

note:   no known conversion for argument 1 from 'const std::vector<unsigned int>*' to 'std::vector<unsigned int>* const&'

我真的需要从 to 复制元素population吗remaining？或者我还能做些什么来避免这种开销？

4

2 回答 2

2

您正在获取 的元素的地址，population以后可能会更改它。这很糟糕，因为您指定population为const.

如果要更改 的元素，则应从定义中删除const关键字population，然后使用iterator代替.const_iteratorpopulation

于 2012-12-06T17:53:31.163 回答
1

尝试

std::vector<const std::vector<unsigned int> *> remaining;
于 2012-12-06T17:56:54.463 回答