C ++如何使用头文件中的cpp文件中的函数

Question

I have a class in a header file called bitarray.h and a corresponding bitarray.cpp and I also have a sieve.h. The sieve.h and bitarray.cpp #includes the bitarray.h and sieve.h only has a function void Sieve(BitArray a). I would like to call Set() and Unset() which are declared in bitarray.h and defined in bitarray.cpp from the Sieve function but it will not let me. How do I fix this.

    //sieve.h
    #include "bitarray.h"
    #include <cmath>

    using namespace std;

    void Sieve(BitArray a)
    {
   //initialize all to 1
   for (int i = 0; i < (a.arraySize*a.unsChar*8); i++)
   {
    a.Set(i);
   }

   //unset 0 and 1 becasue they are never prime
   a.Unset(0);
   a.Unset(1);
   //leave 2 as a 1
       /*for (int i = 2; i < (a.arraySize*a.unsChar*8); i++)
    a.Unset(2*i);*/
    }

Answer 1

Those functions, unless declared in the bitarray.h header, are local to the bitarray.cpp . If you want access to them in sieve.h , declare them in the bitarray.h header, or in another file accessible by sieve.cpp / sieve.h .

// bitarray.h
class BitArray
{
public:
  void Set(); // Example.
  void Unset(); // Example.
};

// sieve.h
#include bitarray.h
void Sieve(BitArray a)
{
  a.Set();
  a.Unset();
}

EDIT:

I'm pretty certain that the issue you're having, is that you're not seeing changes to your BitArray object because you're passing a copy of the original . Any changes you make to it in the Sieve() function won't be reflected in the original object.

Try passing the BitArray object by reference:

void Sieve(BitArray& a)
{
  ...