使用二叉搜索树定义运算符 == 和运算符>时出错

我正在编写一个程序，该程序读取用户输入的文本文件，创建用户输入的文本文件，为用户想要的文本文件命名，然后对文本文件进行排序，对用户输入的阈值以上的单词进行排序，并显示单词及其在用户指定的输出文件中被找到的次数。我有大部分的代码完成，但我得到一个编译器错误在这里的样本输出，错误和代码

输入命令文件的名称;按return键。伦理观输入输出文件的名称;按return键。history.out输入试运行名称;按return键。样本输入要考虑的最小尺寸字。5示例结果(在用户指定的输出文件中找到):样本abacus 4摘要1加1除了2进展1后3

，其中单词是在文本文件中找到的单词，它旁边的数字是它被找到的次数。

编译错误如下:

C:Userskevin jackDesktopprog-4>g++ -o try main.cpp
main.cpp:(.text+0x329) undefined reference to `StrType::PrintToFile(bool, std::basic_ofstream<char, std::char_traits<char> >&)'
:main.cpp:(.text+0x608): undefined reference to `StrType::GetStringFile(bool, InType, std::basic_ifstream<char, std::char_traits<char> >&)'
main.cpp:(.text+0x639): undefined reference to `StrType::LenghtIs()'
main.cpp:(.text+0x6d8): undefined reference to `StrType::GetStringFile(bool, InType, std::basic_ifstream<char, std::char_traits<char> >&)'
collect2: ld returned 1 exit status

我不知道这意味着什么，如果有人知道，请告诉我这里是我的代码

main.cpp

//main.cpp
#include <fstream>
#include "StrType.h"
#include <cstddef>
#include <iostream>
#include <string>
using namespace std;
struct WordType
{
       public:
              StrType word;       
              int count;

};

struct TreeNode
{
       WordType info;
       TreeNode* left;
       TreeNode* right;
};
class ListType
{
      public:
             ListType();
             void InsertOrIncrement (StrType string);
             void Print(std::ofstream&) const;
      private:
              TreeNode* root;
};

ListType::ListType()
{
     root=NULL;
}
void Process(TreeNode*& tree, StrType s)
{
     if(tree == NULL)
     {
         tree = new TreeNode;
         tree->info.word = s;
         tree->info.count = 1;
         tree->left = NULL;
         tree->right = NULL;
     }
     else if (tree->info.word == s)
         tree->info.count++;
     else if (s < tree->info.word)
         Process(tree->left, s);
     else 
         Process(tree->right, s);
}
void ListType::InsertOrIncrement(StrType s)
{
     Process(root, s);
}
void Print (TreeNode* tree, std::ofstream& outFile)
 {
      if (tree!= NULL)
      {
          Print(tree->left, outFile);
          tree->info.word.PrintToFile(true, outFile);
          outFile <<" "<< tree->info.count;
          Print(tree->right, outFile);
      }
 }
 void ListType::Print(std::ofstream& outFile) const
 {
      ::Print(root, outFile);
 }

int main()
{
    using namespace std;
    ListType list;
    string inFileName;
    string outFileName;
    string outputLabel;
    ifstream inFile;
    ofstream outFile;
    StrType string;
    int minimumLenght;
    cout<<"enter in imput file name."<<endl;
    cin>>inFileName;
    inFile.open(inFileName.c_str());
    cout<<"enter name of output file."<<endl;
    cin>>outFileName;
    outFile.open(outFileName.c_str());
    cout<<"enter name of test run."<<endl;
    cin>>outputLabel;
    outFile<< outputLabel << endl;
    cout<<"enter the min word size."<<endl;
    cin>>minimumLenght;
    string.GetStringFile(true, ALPHA_NUM, inFile);
    while(inFile)
    {
         if(string.LenghtIs() >= minimumLenght)
            list.InsertOrIncrement(string);
         string.GetStringFile(true, ALPHA_NUM, inFile);
    }
    list.Print(outFile);
    outFile.close();
    inFile.close();
    return 0;
}

StrType.h

//StrType.h
#include <fstream>
#include <iostream>
const int MAX_CHARS=100;
enum InType{ALPHA_NUM, ALPHA, NON_WHITE, NOT_NEW};
class StrType
{
      public:
             void MakeEmpty();
            void GetString(bool skip, InType charsAllowed);
             void GetStringFile(bool skip, InType charsAllowed,
                std::ifstream& inFile);
             void PrintToScreen(bool newLine);
             void PrintToFile(bool newLine, std::ofstream& outFile);
             int LenghtIs();
             void CopyString(StrType& newString);
              bool operator==(const StrType& other) const;  
              bool operator<(const StrType& other) const;


      private:
              char letters[MAX_CHARS + 1];
};
bool StrType::operator==(const StrType& other) const  
{  
    return (strcmp(letters, other.letters) == 0);  
}  
bool StrType::operator<(const StrType& other) const  
{  
    return (strcmp(letters, other.letters) < 0);  
}  
void StrType::MakeEmpty()
{
     letters[0] ='';
}

我试图重载==和>操作符。我在类StrType中声明它，并在它下面定义它，但我不确定我是否正确地定义它，甚至在正确的位置!如有任何帮助，不胜感激