Language: C++

#include <iostream>


int main(){
int a,b;
char op;

while(1){

std::cin>>a>>op>>b;
if(op == '?'){
break;
} else if(op == '+'){
???std::cout<<a+b<<"\n";
} else if(op == '-'){
???std::cout<<a-b<<"\n";
} else if( op == '*'){
???std::cout<<a*b<<"\n";
} else if(op == '/'){
???std::cout<<a/b<<"\n";
} else {
???break;
}

}

return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:1: error: expected primary-expression before '?' token
   14 | ???std::cout<<a+b<<"\n";
      | ^
a.cc:14:2: error: expected primary-expression before '?' token
   14 | ???std::cout<<a+b<<"\n";
      |  ^
a.cc:14:3: error: expected primary-expression before '?' token
   14 | ???std::cout<<a+b<<"\n";
      |   ^
a.cc:14:24: error: expected ':' before ';' token
   14 | ???std::cout<<a+b<<"\n";
      |                        ^
      |                        :
a.cc:14:24: error: expected primary-expression before ';' token
a.cc:14:24: error: expected ':' before ';' token
   14 | ???std::cout<<a+b<<"\n";
      |                        ^
      |                        :
a.cc:14:24: error: expected primary-expression before ';' token
a.cc:14:24: error: expected ':' before ';' token
   14 | ???std::cout<<a+b<<"\n";
      |                        ^
      |                        :
a.cc:14:24: error: expected primary-expression before ';' token
a.cc:16:1: error: expected primary-expression before '?' token
   16 | ???std::cout<<a-b<<"\n";
      | ^
a.cc:16:2: error: expected primary-expression before '?' token
   16 | ???std::cout<<a-b<<"\n";
      |  ^
a.cc:16:3: error: expected primary-expression before '?' token
   16 | ???std::cout<<a-b<<"\n";
      |   ^
a.cc:16:24: error: expected ':' before ';' token
   16 | ???std::cout<<a-b<<"\n";
      |                        ^
      |                        :
a.cc:16:24: error: expected primary-expression before ';' token
a.cc:16:24: error: expected ':' before ';' token
   16 | ???std::cout<<a-b<<"\n";
      |                        ^
      |                        :
a.cc:16:24: error: expected primary-expression before ';' token
a.cc:16:24: error: expected ':' before ';' token
   16 | ???std::cout<<a-b<<"\n";
      |                        ^
      |                        :
a.cc:16:24: error: expected primary-expression before ';' token
a.cc:18:1: error: expected primary-expression before '?' token
   18 | ???std::cout<<a*b<<"\n";
      | ^
a.cc:18:2: error: expected primary-expression before '?' token
   18 | ???std::cout<<a*b<<"\n";
      |  ^
a.cc:18:3: error: expected primary-expression before '?' token
   18 | ???std::cout<<a*b<<"\n";
      |   ^
a.cc:18:24: error: expected ':' before ';' token
   18 | ???std::cout<<a*b<<"\n";
      |                        ^
      |                        :
a.cc:18:24: error: expected primary-expression before ';' token
a.cc:18:24: error: expected ':' before ';' token
   18 | ???std::cout<<a*b<<"\n";
      |                        ^
      |                        :
a.cc:18:24: error: expected primary-expression before ';' token
a.cc:18:24: error: expected ':' before ';' token
   18 | ???std::cout<<a*b<<"\n";
      |                        ^
      |                        :
a.cc:18:24: error: expected primary-expression before ';' token
a.cc:20:1: error: expected primary-expression before '?' token
   20 | ???std::cout<<a/b<<"\n";
      | ^
a.cc:20:2: error: expected primary-expression before '?' token
   20 | ???std::cout<<a/b<<"\n";
      |  ^
a.cc:20:3: error: expected primary-expression before '?' token
   20 | ???std::cout<<a/b<<"\n";
      |   ^
a.cc:20:24: error: expected ':' before ';' token
   20 | ???std::cout<<a/b<<"\n";
      |                        ^
      |                        :
a.cc:20:24: error: expected primary-expression before ';' token
a.cc:20:24: error: expected ':' before ';' token
   20 | ???std::cout<<a/b<<"\n";
      |                        ^
      |                        :
a.cc:20:24: error: expected primary-expression before ';' token
a.cc:20:24: error: expected ':' before ';' token
   20 | ???std::cout<<a/b<<"\n";
      |                        ^
      |                        :
a.cc:20:24: error: expected primary-expression before ';' token
a.cc:22:1: error: expected primary-expression before '?' token
   22 | ???break;
      | ^
a.cc:22:2: error: expected primary-expression before '?' token
   22 | ???break;
      |  ^
a.cc:22:3: error: expected primary-expression before '?' token
   22 | ???break;
      |   ^
a.cc:22:4: error: expected primary-expression before 'break'
   22 | ???break;
      |    ^~~~~
a.cc:22:4: error: expected ':' before 'break'
   22 | ???break;
      |    ^~~~~
      |    :
a.cc:22:4: error: expected primary-expression before 'break'
   22 | ???break;
      |    ^~~~~
a.cc:22:4: error: expected ':' before 'break'
   22 | ???break;
      |    ^~~~~
      |    :
a.cc:22:4: error: expected primary-expression before 'break'
   22 | ???break;
      |    ^~~~~
a.cc:22:4: error: expected ':' before 'break'
   22 | ???break;
      |    ^~~~~
      |    :
a.cc:22:4: error: expected primary-expression before 'break'
   22 | ???break;
      |    ^~~~~