View Compilation Error

0_0_13147046_6275.cpp: In function 'int main()':
0_0_13147046_6275.cpp:13:16: error: 'isprime' was not declared in this scope
   if (isprime(i))
                ^
0_0_13147046_6275.cpp:26:9: error: 'ring' was not declared in this scope
   ring(1);
         ^
0_0_13147046_6275.cpp: In function 'void isprime(int)':
0_0_13147046_6275.cpp:40:11: error: return-statement with a value, in function returning 'void' [-fpermissive]
    return 0;
           ^
0_0_13147046_6275.cpp:42:9: error: return-statement with a value, in function returning 'void' [-fpermissive]
  return 1;
         ^
0_0_13147046_6275.cpp: In function 'void ring(int)':
0_0_13147046_6275.cpp:49:11: error: 'n' was not declared in this scope
  if (x == n && isprime[a[0]+a[n-1]])
           ^
0_0_13147046_6275.cpp:62:27: error: 'n' was not declared in this scope
   if ( isprime[prime[i]-a[n-1]] && prime[i]-a[n-1] > 1 && sign[i] == 1)
                           ^