string.substr() function

1 Introduction

 A. Function prototype:

  return the substring above the position [ pos, pos + count ) on the string string

2. Analysis

 A. Header file: iostream

 B. Use detailed analysis:

    string s = "abcdef";

  1. If both parameters are omitted, the entire string will be returned by default

    cout << s.substr() << endl; // abcdef

  2. If the second parameter is omitted, the default value of the second parameter is the string size() - pos (default to the end of the string)

    cout << s.substr(2) << endl; // cdef

  3. Out of bounds processing The first parameter out of bounds (too small/too large) will report an error, and the second parameter out of bounds will directly default to the end of the string

    cout << s.substr(-1) << ' ' << s.substr(7) << endl; // 抛出错误异常
    cout << s.substr(2, 100) <<endl; // cdef

3. use

#include<iostream>
#include<cstring>
using namespace std;

int main(){
    
    
    string s = "abcdef";
    cout << s.substr() << endl; // abcdef
    cout << s.substr(2) << endl; // cdef
    // cout << s.substr(-1) << ' ' << s.substr(7) << endl; // 抛出错误异常
    cout << s.substr(2, 100) <<endl; // cdef

}