View Compilation Error

0_0_37307240_32171.cpp:5:5: error: expected constructor, destructor, or type conversion before '(' token
 sort(a + 1, a + n + 1);
     ^
0_0_37307240_32171.cpp: In function 'int main()':
0_0_37307240_32171.cpp:9:21: error: 'bubble_sort' was not declared in this scope
         bubble_sort();
                     ^