std向量与运算符不匹配==

我陷入了这个错误：

gcc.compile.c ++ Physics / HelicityAmplitude / bin / gcc-4.8.3 / debug / HelicityDecayTree.o在/cvmfs/cluster/gcc/gcc-4.8.3/include/c++/4.8.3/algorithm:62包含的文件中：0，来自/cluster/compwa_externals/boost_1_55_0/include/boost/move/algorithm.hpp:23，来自/cluster/compwa_externals/boost_1_55_0/include/boost/move/move.hpp:24，来自/ cluster / compwa_externals / boost_1_55_0 /include/boost/unorder/detail/util.hpp:19，来自/cluster/compwa_externals/boost_1_55_0/include/boost/unorder/detail/buckets.hpp:14，来自/ cluster / compwa_externals / boost_1_55_0 / include / boost / unordered /detail/table.hpp:10，来自/cluster/compwa_externals/boost_1_55_0/include/boost/unorder/detail/equivalent.hpp:14，来自/cluster/compwa_externals/boost_1_55_0/include/boost/unordered/unordered_set.hpp:17 ，来自/cluster/compwa_externals/boost_1_55_0/include/boost/unordered_set.hpp:16，来自/cluster/compwa_externals/boost_1_55_0/include/boost/graph/adjacency_list.hpp:21，来自Physics / HelicityAmplitude / HelicityDecayTree.hpp：17，来自Physics / HelicityAmplitude / HelicityDecayTree.cpp：12：

/cvmfs/cluster/gcc/gcc-4.8.3/include/c++/4.8.3/bits/stl_algo.h：在'_RandomAccessIterator std :: __ find（_RandomAccessIterator，_RandomAccessIterator，const _Tp＆，std :: random_access_iterator_tag）的实例中使用_RandomAccessIterator = __gnu_cxx :: __ normal_iterator>; _Tp = HelicityFormalism :: ParticleState]'：

/cvmfs/cluster/gcc/gcc-4.8.3/include/c++/4.8.3/bits/stl_algo.h:4441:45：要求来自'_IIter std :: find（_IIter，_IIter，const _Tp＆）[带有_IIter = __gnu_cxx :: __ normal_iterato r>; _Tp = HelicityFormalism :: ParticleState]'Physics / HelicityAmplitude / HelicityDecayTree.cpp：59：61：从此处需要

/cvmfs/cluster/gcc/gcc-4.8.3/include/c++/4.8.3/bits/stl_algo.h:166:17：错误：'operator =='不匹配（操作数类型为'HelicityFormalism :: ParticleState '和'const Helicit yFormalism :: ParticleState'）如果（* __ first == __val）

我看到他正在要求对ParticleState进行const与非const的比较。但是我真的不明白他为什么要进行这种比较。我的相关代码如下：

该类的标题：

class HelicityDecayTree {
  boost::adjacency_list<> decay_tree_;
  std::vector<ParticleState> particles_;

public:
  void createDecay(const ParticleState &mother,
  const ParticleStatePair &daughters);
}

以及该成员函数的来源：

void HelicityDecayTree::createDecay(const ParticleState &mother,
    const ParticleStatePair &daughters) {
  // add particles to the list
  unsigned int mother_vector_index;
  unsigned int daughter1_vector_index;
  unsigned int daughter2_vector_index;

  if (std::find(particles_.begin(), particles_.end(), mother)
      == particles_.end()) {
    mother_vector_index = particles_.size();
    particles_.push_back(mother);
  }
  else {
    mother_vector_index = std::distance(particles_.begin(),
        std::find(particles_.begin(), particles_.end(), mother));
  }
  if (std::find(particles_.begin(), particles_.end(), daughters.first)
      == particles_.end()) {
    daughter1_vector_index = particles_.size();
    particles_.push_back(daughters.first);
  }
  else {
    daughter1_vector_index = std::distance(particles_.begin(),
        std::find(particles_.begin(), particles_.end(), daughters.first));
  }
  if (std::find(particles_.begin(), particles_.end(), daughters.second)
      == particles_.end()) {
    daughter2_vector_index = particles_.size();
    particles_.push_back(daughters.second);
  }
  else {
    daughter2_vector_index = std::distance(particles_.begin(),
        std::find(particles_.begin(), particles_.end(), daughters.second));
  }

  // then make the correct inserts into the vector and link appropriately
  boost::add_edge(mother_vector_index, daughter1_vector_index, decay_tree_);
  boost::add_edge(mother_vector_index, daughter2_vector_index, decay_tree_);
}

和ParticleState结构：

struct ParticleState {
  int particle_id_;
  std::string name_;
  Spin J_;
  Spin M_;
};

Afaiu他应该为两个const ParticleStates合成operator ==，但是由于某种原因，find方法要求为1个参数提供非const版本。

提前谢谢，史蒂夫