I get an error on this line: rev(s[s.length]);

[Bopaki]

I am trying to compile this program and I get this error:

20 10 C:\Dev-Cpp\MalikChapter6\reverseString.cpp [Error] no match for 'operator[]' (operand types are 'std::string {aka std::basic_string<char>}' and '<unresolved overloaded function type>')

  #include<iostream>
#include<cstring>
#include<cctype>

string rev(string s);

using namespace std;

int main() {
	
	string s;
	cout<<"\nEnter a string: \n";
	cin >> s;
	cout<<"The string in reverse is: " ;
	 rev(s) ;
}

string rev(string s) {
  if (!s.empty()) {
    rev(s[s.length]);
  }
  cout<< s[0];
}

[coder777]

Add the parentheses after length:

rev(s[s.length()]);

Actually it is out of bounds add -1.

Also rev(...) needs to return a string.

[JLBorges]

std::string rev_1( std::string str )
{
    const auto sz = str.size() ;
    if( sz < 2 ) return str ;
    else return str.back() + rev_1( str.substr( 1, sz-2 ) ) + str.front() ;
}

std::string rev_2( std::string str ) { return { str.rbegin(), str.rend() } ; }

std::string rev_3( std::string str )
{
    std::reverse( str.begin(), str.end() ) ;
    return str ;
}

[Bopaki]

Thank you all!!!
It worked so well!!!!!!!!!