带有 const 参数的方法不接受非 const 参数

Method with const parameter does not accept non-const parameter?

本文关键字：参数 const 不接受 带有 方法      更新时间：2023-10-16

此代码无法编译：

ErrorTolerantSearch e;
e.readStringsFromFile("test.txt");
e.buildQgramIndex(3);
vector<map<uint, uint>*> lists;
lists.push_back(&e._qgramIndex["ret"]); // ignore this, assume container not empty
lists.push_back(&e._qgramIndex["coo"]); // ignore this, assume container not empty
map<uint, uint> resunion = e.computeUnion(lists); // <-- this makes problems

这是标题的一部分

class ErrorTolerantSearch {
 public:
  void readStringsFromFile(string fileName);
  void buildQgramIndex(uint  q);
  map<uint, uint> computeUnion(const vector<const map<uint, uint>*> & lists);
  map<string, map<uint, uint> > _qgramIndex;
};

这是编译器给出的错误：

ErrorTolerantSearchTest.cpp: In member function ‘virtual void ErrorTolerantSearchTest_computeUnion_Test::TestBody()’:
ErrorTolerantSearchTest.cpp:89:50: error: no matching function for call to ‘ErrorTolerantSearch::computeUnion(std::vector<std::map<unsigned int, unsigned int>*>&)’
ErrorTolerantSearchTest.cpp:89:50: note: candidate is:
In file included from ErrorTolerantSearchTest.cpp:36:0:
./ErrorTolerantSearch.h:56:19: note: std::map<unsigned int, unsigned int> ErrorTolerantSearch::computeUnion(const std::vector<const std::map<unsigned int, unsigned int>*>&)
./ErrorTolerantSearch.h:56:19: note:   no known conversion for argument 1 from ‘std::vector<std::map<unsigned int, unsigned int>*>’ to ‘const std::vector<const std::map<unsigned int, unsigned int>*>&’
make[1]: *** [ErrorTolerantSearchTest] Fehler 1

但问题出在哪里呢？我不明白。我从来没有遇到过通过引用将非常量变量传递给带有常量参数的函数的问题。

std::vector<const T>不

等于std::vector<T>，也不能转换为它。

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