View Compilation Error

0_0_23181396_18880.cpp: In function 'int calculate(char, int)':
0_0_23181396_18880.cpp:30:12: error: a function-definition is not allowed here before '{' token
 int main() {
            ^
0_0_23181396_18880.cpp:50:1: error: expected '}' at end of input
 }
 ^