how can i calculate 'the sizeof pointer's array

[alsade]

im trying to create a function that will execute a for loop as many times as the size of array which contains pointers to structobjects.
the only thing i can send to the function its a pointer to the beginning of the array.

this is my struct:

struct Student
{
	unsigned int id;
	char first[20];
	char last[20];
	char email[100];
};

and this is the function:

int length(Student* Beginning of th array )
{
   int size=0;
   for (int i=0;i</*size of Student's array*/;i++)
        {
          size++;
        }
}

is there a way to do it??

thx.

[nvrmnd]

I recommend to use std::array<> and just call .size() member function and it will return the number of elements inside it :

#include <array>

struct Student
{
  unsigned id;
  // ...
};

int main()
{
  using std::array;
  array<Student, 10> student;

  for ( size_t i = 0; i < student.size(); ++i ) {
    student[ i ].id = i;
  }
}

unfortunately, afaik, there is no way to know the size of the array by only passing a pointer to the beginning of the array.
You must use some form of syntactic sugar and template deduction technique :

struct Student
{
    unsigned id;
}

// can work with any type of array (char, float, double, etc...)
template <typename T, size_t N>
constexpr size_t length ( T (&)[ N ] ) // C++11 (constexpr so that this function is called at compile-ime
{ return N; }

int main()
{
  Student student[ 50 ];

  for ( size_t i = 0; i < length(student); ++i ) {
    student[ i ].id = i;
}

NOTE you must enable c++11 mode in ur compiler to use std::array<> and constexpr, -std=c++11 or -std=c++0x on GCC