21.6. Arrays, Functions, and Return Values

21.6. Arrays, Functions, and Return Values
	Chapter 21. Memory Access

[ fromfile: memoryaccess.xml id: arraysandfunctions ]

As in C, the declared return type of a function cannot be array (e.g., it cannot look like int[] or char[] or Point[]).
Returning (addresses of) arrays from functions that are pointer-typed is allowed.
not recommended in the public interface of a class.

You have seen that an array is a piece of unprotected memory.
A class that encapsulates that memory should not have public member functions that return pointers to it.

Arrays are never passed to functions by value; i.e., the array elements are not copied.
If a function is called with an array in its argument list, for example,
```
   int a[] = {10, 11, 12, 13, 14, 15};
   void f(int a[]) {
      [ ... ]
   }
      [ ... ]
   f(a);
  
```
then the actual value passed is only a pointer to the first element in the array.
Example 21.5 demonstrates this, by showing functions that pass and return arrays.

Example 21.5. src/arrays/returningpointers.cpp


#include <assert.h>

int paramSize;

void bar(int* integers) {
    integers[2]=3;                      
}

int* foo(int arrayparameter[]) {
    using namespace std;
    paramSize = sizeof(arrayparameter);
    bar(arrayparameter);                
    return arrayparameter;              
}
    
int main(int argc, char** argv) {
    int intarray2[40] = {9,9,9,9,9,9,9,2,1};
    char chararray[20] = "Hello World"; 
    int intarray1[20];                  
    int* retval;                        

//  intarray1 = foo(intarray2);         

    retval = foo(intarray2);
    assert (retval[2] == 3);
    assert (retval[2] = intarray2[2]);
    assert (retval == intarray2);
    int refSize = getSize(intarray2);
    assert(refSize == paramSize);
    return 0;
}

	Change the third element in the incoming array.
	Pass an array by pointer to a function.
	Return an array as a pointer from a function.
	Special syntax for initializing char array.
	Uninitialized memory.
	Uninitialized pointer.
	Error, intarray1 is like a char* const, it cannot be assigned to.


21.5. Pointer Arithmetic		21.7. Different Kinds of Arrays