/in/foo.cc: In function 'bool isOperator(char)':
/in/foo.cc:8:62: error: expected ';' before '('
     return c == '+' || c == '-' || c == '*' || c == '^' || c '(' || c == ')';
                                                              ^~~
/in/foo.cc:8:66: warning: statement has no effect [-Wunused-value]
     return c == '+' || c == '-' || c == '*' || c == '^' || c '(' || c == ')';
                                                              ~~~~^~~~~~~~~~~
/in/foo.cc: At global scope:
/in/foo.cc:23:34: error: expected ')'
 std::string infixToPostfix(const std::& infix) {
                                  ^~~
/in/foo.cc:23:34: error: expected initializer