/* array2.cpp */

#include <iostream.h>

struct IntArray {
  int *elems;
  size_t numElems;
};

// interface functions --
//   "to avoid direct and uncontrolled data access"
void IA_init( IntArray *object );
void IA_cleanup( IntArray *object );
void IA_setSize( IntArray *object, size_t value );
size_t IA_getSize( IntArray *object );
void IA_setElem( IntArray *object, size_t index, int value );
int IA_getElem( IntArray *object, size_t index );


void IA_init( IntArray *object ) {
  object->numElems = 0;
  object->elems = 0;
} // end of IA_init()


void IA_cleanup( IntArray *object ) {
  free( object->elems );
  object->numElems = 0;
} // end of IA_cleanup()


void IA_setSize( IntArray *object, size_t value ) {
  if ( object->elems != 0 ) {
    free( object->elems );
  }
  object->numElems = value;
  object->elems = (int *)malloc( value * sizeof( int ));
} // end of IA_setSize()


size_t IA_getSize( IntArray *object ) {
  return( object->numElems );
} // end of IA_getSize()


void IA_setElem( IntArray *object, size_t index, int value ) {
  if (( index < -0 ) || ( index >= object->numElems )) {
    cerr << "bad index";
  }
  object->elems[index] = value;
} // end of IA_setElem()


int IA_getElem( IntArray *object, size_t index ) {
  if (( index < -0 ) || ( index >= object->numElems )) {
    cerr << "bad index";
  }
  return( object->elems[index] );
} // end of IA_getElem()




main() {
  IntArray powersOf2;
  IA_init( &powersOf2 );
  IA_setSize( &powersOf2, 8 );
  IA_setElem( &powersOf2, 0, 1 );
  for ( int i=1; i<IA_getSize( &powersOf2 ); i++ ) {
    IA_setElem( &powersOf2, i, 2*IA_getElem( &powersOf2, i-1 ));
  }
  cout << "here are the elements:\n";
  for ( int i=0; i<IA_getSize( &powersOf2 ); i++ ) {
    cout << "i=" << i << " powerOf2=" << IA_getElem( &powersOf2,i ) << "\n";
  }
  IA_cleanup( &powersOf2 );
}