/*std*/实现mstring类

//实现mstring类，
//未实现友元函数+,<<,>>
  1 #include<cstring>
  2 #include<iostream>
  3 #include<istream>
  4 #include<ostream>
  5 class mstring{
  6     friend mstring& operator+(const mstring&str1,const mstring&str2);
  7     friend mstring& operator+(const char*str1,const mstring&str2);
  8     friend mstring& operator+(const mstring&str1,const char*str2);
  9     friend std::ostream&operator<<(std::ostream&os,const mstring&str);
 10     friend std::istream&operator>>(std::istream&is,mstring&str);
 11     public:
 12         mstring();
 13         mstring(char*str);
 14         mstring(const mstring& str);
 15         mstring(int n);
 16         ~mstring(){
 17             delete[]m_data;
 18         }
 19         mstring& operator=(char*str);
 20         mstring& operator=(const mstring&str);
 21         bool operator<(const mstring&str)const;
 22         bool operator>(const mstring&str)const;
 23         bool operator==(const mstring&str)const;
 24         void printf()const;
 25         int get_length()const{
 26             return strlen(m_data);
 27         }
 28         mstring substring(int i,int j)const;
 29     private:
 30         char*m_data;
 31             
 32 };
 33 
 34 mstring::mstring(){
 35     m_data=new char;
 36     *m_data=‘\0‘;
 37 }
 38 mstring::mstring(char*str){
 39     m_data=new char[strlen(str)+1];
 40     strcpy(m_data,str);    
 41 }
 42 mstring::mstring(const mstring&str){
 43     m_data=new char[strlen(str.m_data)+1];
 44     strcpy(m_data,str.m_data);
 45 }
 46 mstring::mstring(int n){
 47     m_data=new char[n+1];
 48     int i=0;
 49     for(i=0;i<n;i++){
 50         m_data[i]=‘0‘;
 51     }
 52     m_data[n]=‘\0‘;
 53 }
 54 mstring& mstring::operator=(char*str){
 55     delete [] m_data;
 56     m_data=NULL;
 57     m_data=new char[strlen(str)+1];
 58     strcpy(m_data,str);    
 59     return *this;
 60 }
 61 mstring& mstring::operator=(const mstring&str){
 62     if(this==&str) return *this;
 63     delete []m_data;
 64     m_data=NULL;
 65     m_data=new char[strlen(str.m_data)+1];
 66     strcpy(m_data,str.m_data);
 67     return *this;
 68 }
 69 bool mstring::operator<(const mstring&str)const{
 70     if(strcmp(this->m_data,str.m_data)<0) return true;
 71     else return false;
 72 }
 73 bool mstring::operator>(const mstring&str)const{
 74     if(strcmp(this->m_data,str.m_data)>0) return true;
 75     else return false;
 76 }
 77 bool mstring::operator==(const mstring&str)const{
 78 if(strcmp(this->m_data,str.m_data)==0) return true;
 79     else return false;
 80 }
 81 
 82 //mstring operator+(const mstring&str1,const mstring&str2){}
 83 
 84 //mstring operator+(const char*str1,const mstring&str2){}
 85 
 86 //mstring operator+(const mstring&str1,const char*str2){}
 87 
 88 //ostream&operator<<(ostream&str,const mstring&str){}
 89 
 90 //istream&operator>>(istream&str,mstring&str){}
 91 
 92 void mstring::printf()const{
 93     for(int i=0;m_data[i]!=0;i++){
 94                 std::cout<<m_data[i];
 95     }
 96     std::cout<<std::endl;
 97 }
 98 
 99 mstring mstring::substring(int i,int j)const{
100     int strlength=strlen(this->m_data);
101     if(i>j||i>strlength-1||j<0){
102         mstring mtemp;
103         return mtemp;
104     }
105     if(i<0) i=0;
106     if(j>strlength-1) j=strlength-1;
107     mstring mtemp(j-i+1); 
108     int index=0,k=0;
109     for(index=0;index<=strlength-1;index++){
110         if(index>=i&&index<=j)
111         {
112             mtemp.m_data[k++]=this->m_data[index];
113         }
114     }
115     return mtemp;
116 }
117 
118 int main(){
119     mstring ms,ms2,ms3;
120     ms="adbc";
121     ms2=ms;
122     ms.printf();
123     ms2.printf();
124     std::cout<<ms.get_length();
125     std::cout<<std::endl;
126     ms3=ms2.substring(1,5);
127     ms3.printf();
128     return 0;
129 }