c++ - Array Related Error - Invalid Types..? -

i making simple program related arrays. code:

#include <iostream> #include <cmath> using namespace std;  int main() { int a; cout << "please enter length of array: " << endl; cin >> a; bool array[a];  (int n = 0; n < a; n++) {     array[n] = true;  } array[0] = false; array[1] = false; (int k = 2; k < a; k++) {         if (array[k] == true){      (int = 0; pow(k,2)+ i*k < a; i++) {         array[ pow(k,2) + * k] = false;               }         }  }      (int j = 0 ; j < ; j++){         if (array[j] == true){         cout << j <<endl;         }     } 

}

i error in line

array[ pow(k,2) + * k] = false; 

it says

"invalid types" ||=== build: debug in test (compiler: gnu gcc compiler) ===| c:\users\momo\documents\codeblocks projects\test\main.cpp||in function 'int main()':| c:\users\momo\documents\codeblocks projects\test\main.cpp|21|error: invalid types 'bool [(((sizetype)(((ssizetype)a) + -1)) + 1)][__gnu_cxx::__promote_2<int, int, double, double>::__type {aka double}]' array subscript| ||=== build failed: 1 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===| 

that error. trying switch java c++. such kind of error new me never encountered such error in java. can guys , girls me understand means? , can resolve it? thanks.

welcome! have entered whole new world programming in c++. let me introduce c++ standard library (often called stl) (http://www.cplusplus.com reference). containers want use in everyday life want consider 1 standard library.

in particular instance, cannot instantiate array @ runtime have done above. cannot instantiate array on stack size determined @ runtime. need dynamically allocate memory on heap or use stl container (std::vector<> advised). how have written code

#include <iostream> #include <cmath> #include <vector> using namespace std;  int main() {     int a;     cout << "please enter length of array: " << endl;     cin >> a;     vector<bool> array(a);      (int n = 0; n < a; n++) {         array[n] = true;      }     array[0] = false;     array[1] = false;      (int k = 2; k < a; k++) {         if (array[k] == true){              (int = 0; pow(k,2)+ i*k < a; i++) {                 array[ static_cast<size_t>(pow(k,2) + * k) ] = false;              }         }     }      (int j = 0 ; j < ; j++){         if (array[j] == true){             cout << j <<endl;         }     }       return 0; } 

to explain more here. following line

std::vector<bool> array(n) 

initializes vector (for sake of simplicity) n elements.

more information vector class can found here (http://www.cplusplus.com/reference/vector/vector/?kw=vector)