Language: C++

#include<iostream>
#include<stack>

int main() {
    stack<int> S;
    for (string s; cin >> s&&s != "$";) {
        int a, b;
        switch (s[0]) {
        case '+':
            b = S.top(); S.pop();
            a = S.top(); S.pop();
            S.push(a + b);
            break;
        case '-':
            b = S.top(); S.pop();
            a = S.top(); S.pop();
            S.push(a - b);
            break;
        case '*':
            b = S.top(); S.pop();
            a = S.top(); S.pop();
            S.push(a * b);
            break;
        default:
            S.push(atoi(s.c_str()));
            break;
        }
    }
 
    cout << S.top() << endl;
 
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:5:5: error: 'stack' was not declared in this scope; did you mean 'std::stack'?
    5 |     stack<int> S;
      |     ^~~~~
      |     std::stack
In file included from /usr/include/c++/14/stack:63,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_stack.h:99:11: note: 'std::stack' declared here
   99 |     class stack
      |           ^~~~~
a.cc:5:11: error: expected primary-expression before 'int'
    5 |     stack<int> S;
      |           ^~~
a.cc:6:10: error: 'string' was not declared in this scope
    6 |     for (string s; cin >> s&&s != "$";) {
      |          ^~~~~~
a.cc:6:10: note: suggested alternatives:
In file included from /usr/include/c++/14/iosfwd:41,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
In file included from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44:
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:6:20: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |     for (string s; cin >> s&&s != "$";) {
      |                    ^~~
      |                    std::cin
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:27: error: 's' was not declared in this scope
    6 |     for (string s; cin >> s&&s != "$";) {
      |                           ^
a.cc:10:17: error: 'S' was not declared in this scope
   10 |             b = S.top(); S.pop();
      |                 ^
a.cc:30:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   30 |     cout << S.top() << endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:30:13: error: 'S' was not declared in this scope
   30 |     cout << S.top() << endl;
      |             ^
a.cc:30:24: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   30 |     cout << S.top() << endl;
      |                        ^~~~
      |                        std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~