c++ - C++ 中的未知错误消息 C2440

Question

所以当我尝试在 Unix 中运行我的头文件时，我收到一条错误消息“error C2440: 'initializing' : cannot convert from 'std::vector<_Ty> *' to 'std::vector<_Ty> '”。我想我收到这个错误是因为我在 allOperations 中调用了“转换”，但我不确定。这是头文件:

#include <iostream>
#include <vector>
#include <string>
#include <fstream> //library for files
#include <cctype>
#include <algorithm>
#include <iterator>
#include <sstream>
#include <typeinfo>


using namespace std;

template <class T>
void alloc3DArray(T *** &x, int numberOfRows, int numberOfColumns,int numberOfDepth  )
{

 int i=0;
 int j=0;
 int k=0;


 // allocate an array for array of arrays
  x = new T ** [numberOfRows];


 // Allocate an array for each element of the first array
   for(i = 0; i < numberOfRows; i++)
    {

        x[i] = new T *[numberOfColumns];

  // Allocate an array of T for each element of this array
        for(j = 0; j < numberOfColumns; j++)
        {

            x[i][j] = new T [numberOfDepth];

   // Specify an initial value 
   for(int k = 0; k < numberOfDepth; ++k)
   {
    x[i][j][k] = -1;


   }


        }
    }

}

template <class T>
void dealloc3DArray(T *** &x, int numberOfRows, int numberOfColumns )

{
 // Check if it exeists 
 if(!x) //it does not exist
         exit(1);



    for (int i = 0; i < numberOfRows; ++i) 
    {
   for (int j = 0; j < numberOfColumns; ++j)

        {
    //delete innest
            delete [] x[i][j]; 
        }

   //delete columns
        delete [] x[i];
    }
 //delete first array
    delete [] x;
}

template <class T>
const vector<T>  allOperationsNotWorking(T *** &myArray1, T *** &myArray2,  T *** &myArray3,int numberOfRows, int numberOfColumns,int numberOfDepth  )

{
    int i=0;
 int j=0;
 int k=0;

    int size = numberOfRows * numberOfColumns * numberOfDepth; //find vector size
    vector<T> &myvector = vector<T>(size);// create a vector
    //vector<T>::const_iterator it;// const_iterator is faster than iterator
    for(i = 0; i < numberOfRows; i++)
   for(j = 0; j < numberOfColumns; j++)
    for(k = 0; k < numberOfDepth; k++){

     myArray3[i][j][k] =myArray1[i][j][k]+myArray2[i][j][k];

     myvector.push_back(myArray3[i][j][k]);


    }
     return myvector;


}

vector<string>  allOperationsString(string *** &myArray1, string *** &myArray2,  string *** &myArray3,int numberOfRows, int numberOfColumns,int numberOfDepth  )

{
    int i=0;
 int j=0;
 int k=0;

    int size = numberOfRows * numberOfColumns * numberOfDepth; //find vector size
    vector<string> myvector = vector<string>(size);// create a vector
    //vector<T>::const_iterator it;// const_iterator is faster than iterator
    for(i = 0; i < numberOfRows; i++)
   for(j = 0; j < numberOfColumns; j++)
    for(k = 0; k < numberOfDepth; k++){

     myArray3[i][j][k] =myArray1[i][j][k]+myArray2[i][j][k];

     myvector.push_back(myArray3[i][j][k]);


    }
     return myvector;


}

template <class T>
vector<T> isWord(vector<T> &stringVector, vector<T> &goodOnes,vector<T> &badOnes, vector<T> &dict)
{
    vector<int> strV;


 if (typeid(stringVector).name()== typeid(strV).name()){

 //if (typeid(stringVector)==int){
  ofstream badFile; //  declare and object as output file  using ofstream
  cout << " Illegal Vector" << endl;
  badFile.open ("hw1bout2.txt", ios::app);
  badFile << "Illegal Vector" << endl;
  badFile.close();
  return badOnes;
  }

 int i=0;
 int j=0;
 int FIRSTSIZE=stringVector.size();
 int SECONDSIZE = dict.size();
 std::string sInput="";
 std::string sDict="";

 sort(stringVector.begin(), stringVector.end());//sort() uses quicksort from the algorith library

  for(int i=0, j=0; i < FIRSTSIZE && j < SECONDSIZE; ){
   sInput=stringVector[i];


   std::transform(sInput.begin(), sInput.end(), sInput.begin(), std::toupper); //convert input word to upper

   sDict=dict[j];


   if(sInput.compare(sDict) == 0) {
   goodOnes.push_back(stringVector[i]); //write good word to vector

   i++;//advance one position in string vector
   j++;//advance one position in dictionary
    }

  else if(stringVector[i] < dict[j] && FIRSTSIZE < SECONDSIZE){// wrods did not match
   if (stringVector[i].size() >0) badOnes.push_back(stringVector[i]); //write bad word to vector if not empty string
   i++;//advance one position in string vector
   }

  else{
   j++;//advance one position in dictionary
    }
}



 return goodOnes;
}

template<class T >    
vector<string> isWord(vector<int> &stringVector, vector<string> &goodOnes,vector<string> &badOnes, vector<string> &dict)
{

 vector<int> strV;


 if (typeid(stringVector).name()== typeid(strV).name()){

  badOnes.push_back("Illegal Vector" );
 }
  return badOnes;

}

//template<class T>
vector<int>  allOperations(int *** &myArray1, int *** &myArray2,  int *** &myArray3,int numberOfRows, int numberOfColumns,int numberOfDepth  )

{
    int i=0;
 int j=0;
 int k=0;

    int size = numberOfRows * numberOfColumns * numberOfDepth; //find vector size
    vector<int> myvector = vector<int>(size);// create a vector
    //const vector<int>& myvector;
    //vector<int>::const_iterator it = myvector.begin();
    vector<int>::const_iterator it;// const_iterator is faster than iterator
    for(i = 0; i < numberOfRows; i++)
   for(j = 0; j < numberOfColumns; j++)
    for(k = 0; k < numberOfDepth; k++){

     myArray3[i][j][k] =myArray1[i][j][k]+myArray2[i][j][k];

     myvector.push_back(myArray3[i][j][k]);


    }
     return myvector;


}

Answer 1

从 g++ 获得的实际错误消息(不是您发布的错误消息)非常清楚地表明 std::transform 的最后一个参数是重载函数的名称。

由于该参数用于模板参数推导，编译器无法选择任何一个重载。我们将通过在强类型上下文中命名重载函数的集合来帮助它:

char (*transformation_fn)(char) = &std::toupper;
std::transform(sInput.begin(), sInput.end(), sInput.begin(), transformation_fn);

通过此更改，the code compiles without errors .