编译器错误"character constant too long for its type" 。怎么了？

我有一些代码正在尝试处理…

#include <iostream>
#include <string>
int main()
{
  std::cout << "Hello. Welcome to Delicious Drive Up. What would you like to order?n";
  std::cout << "nOur menu is-";
  std::cout << "...";
  std::cout << "nOrder here > ";
  std::string choice;
  std::getline(cin, choice);
  if (choice == 'hamburger' || choice == 'Hamburger')
  {
      std::cout << "We don't have any ham. Is a Chickenburger all right? y/n. > ";
      std::string opt;
      std::getline(cin, opt);
      if (opt == 'y' || opt == 'Y' || opt == 'yes' || opt = 'Yes')
      {
          std::cout << "Here's your chickenburger.";
      }
  }
}

这是根据我写的Bash脚本改编的，是我的第一个C++程序之一。当我编译这个时，它会出现这些错误。。。

test.cpp:19:15: warning: character constant too long for its type
test.cpp:19:40: warning: character constant too long for its type
test.cpp:23:44: warning: multi-character character constant
test.cpp:23:59: warning: multi-character character constant
test.cpp: In function ‘int main()’:
test.cpp:19: error: no match for ‘operator==’ in ‘choice == 1919378802’
test.cpp:19: error: no match for ‘operator==’ in ‘choice == 1919378802’
test.cpp:23: error: no match for ‘operator==’ in ‘opt == 'y'’
test.cpp:23: error: no match for ‘operator==’ in ‘opt == 'Y'’
test.cpp:23: error: no match for ‘operator==’ in ‘opt == 7955827’

你能解释一下这些是什么意思以及如何修复它们吗？

编辑：我现在收到一条新的错误消息。。。

.test.cpp: In function ‘int main()’:
.test.cpp:23: error: no match for ‘operator||’ in ‘((std::operator== [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](((const std::basic_string<char, std::char_traits<char>, std::allocator<char> >&)((const std::basic_string<char, std::char_traits<char>, std::allocator<char> >*)(& opt))), ((const char*)"y")) || std::operator== [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](((const std::basic_string<char, std::char_traits<char>, std::allocator<char> >&)((const std::basic_string<char, std::char_traits<char>, std::allocator<char> >*)(& opt))), ((const char*)"Y"))) || std::operator== [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](((const std::basic_string<char, std::char_traits<char>, std::allocator<char> >&)((const std::basic_string<char, std::char_traits<char>, std::allocator<char> >*)(& opt))), ((const char*)"yes"))) || opt’
.test.cpp:23: note: candidates are: operator||(bool, bool) <built-in>