Language: C++

#include <iostream>
#include <cstring>
#include <string>

#define MAX_LEN (1000)
#define MAX_Q   (100)

using namespace std;

void all_lower(string str);

int main()
{
    int    q;
    string str;

    do {
        cin >> str;
    } while (str.length() < 1 || str.length() > MAX_LEN || all_lower(str) == 0);

    do {
        cin >> q;
    } while (q < 1 || q > MAX_Q);
    
    for (int i = 0; i < q; i++) {
         int    a, b;
         string ins;
         string p;

         do {
             int num = (cin >> ins >> a >> b >> p);
         } while (a < 0 || b < 0 || a > b || b > str.length() ||
                  (ins == "replace" && b - a + 1 != strlen(p)));
                    
         if (num == 3) {
             if (ins == "print") {
                 cout << str.substr(a, b) << endl;
             } else if (ins == "reverse") {      
                 reverse(a, b);
             } 
         } else if (num == 4) {
             replace(a, b, p);
         }
    }

    return (0);
}

void all_lower(string str)
{
     int i;

     for (i = 0; str[i] != '\0'; i++) {
          if (str[i] < 'a' || str > 'z') {
              break;
          }
     }

     if (str[i] == '\0') {
         return (1);
     } else {
         return (0);
     }
}
    

Compiler output:
a.cc: In function 'int main()':
a.cc:19:75: error: invalid operands of types 'void' and 'int' to binary 'operator=='
   19 |     } while (str.length() < 1 || str.length() > MAX_LEN || all_lower(str) == 0);
      |                                                            ~~~~~~~~~~~~~~ ^~ ~
      |                                                                     |        |
      |                                                                     void     int
a.cc:31:46: error: cannot convert 'std::basic_istream<char>' to 'int' in initialization
   31 |              int num = (cin >> ins >> a >> b >> p);
      |                        ~~~~~~~~~~~~~~~~~~~~~~^~~~~
      |                                              |
      |                                              std::basic_istream<char>
a.cc:33:60: error: cannot convert 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'const char*'
   33 |                   (ins == "replace" && b - a + 1 != strlen(p)));
      |                                                            ^
      |                                                            |
      |                                                            std::string {aka std::__cxx11::basic_string<char>}
In file included from /usr/include/c++/14/cstring:43,
                 from a.cc:2:
/usr/include/string.h:407:35: note:   initializing argument 1 of 'size_t strlen(const char*)'
  407 | extern size_t strlen (const char *__s)
      |                       ~~~~~~~~~~~~^~~
a.cc:35:14: error: 'num' was not declared in this scope; did you mean 'enum'?
   35 |          if (num == 3) {
      |              ^~~
      |              enum
a.cc:39:18: error: 'reverse' was not declared in this scope
   39 |                  reverse(a, b);
      |                  ^~~~~~~
a.cc:42:14: error: 'replace' was not declared in this scope
   42 |              replace(a, b, p);
      |              ^~~~~~~
a.cc: In function 'void all_lower(std::string)':
a.cc:54:35: error: no match for 'operator>' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'char')
   54 |           if (str[i] < 'a' || str > 'z') {
      |                               ~~~ ^ ~~~
      |                               |     |
      |                               |     char
      |                               std::string {aka std::__cxx11::basic_string<char>}
In file included from /usr/include/c++/14/string:48,
                 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,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:462:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator>(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  462 |     operator>(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:462:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
/usr/include/c++/14/bits/stl_iterator.h:507:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator>(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  507 |     operator>(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:507:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
/usr/include/c++/14/bits/stl_iterator.h:1714:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator>(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1714 |     operator>(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1714:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
/usr/include/c++/14/bits/stl_iterator.h:1774:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator>(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1774 |     operator>(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1774:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51:
/usr/include/c++/14/bits/stl_pair.h:1058:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator>(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1058 |     operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1058:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::pair<_T1, _T2>'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:695:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  695 |     operator> (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:695:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   'std::__cxx11::basic_string<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
/usr/include/c++/14/string_view:702:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  702 |     operator> (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:702:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   'std::__cxx11::basic_string<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
/usr/include/c++/14/string_view:710:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  710 |     operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:710:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'char'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
/usr/include/c++/14/bits/basic_string.h:3915:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3915 |     operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3915:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'char'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
/usr/include/c++/14/bits/basic_string.h:3929:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3929 |     operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3929:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   mismatched types 'const _CharT*' and 'char'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
/usr/include/c++/14/bits/basic_string.h:3942:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3942 |     operator>(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3942:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   mismatched types 'const _CharT*' and 'std::__cxx11::basic_string<char>'
   54 |           if (str[i] < 'a' || str > 'z') {
      |                                     ^~~
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2619:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator>(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2619 |     operator>(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2619:5: note:   template argument deduction/substitution failed:
a.cc:54:37: note:   'std::string' {aka