===============================  DEFINITIONS ==============================

Value: 
In computer science, a value is a sequence of bits that is interpreted
according to some data type.

Reference:
In computer science, a reference is an object containing information which
refers to data stored elsewhere, as opposed to containing the data
itself. Accessing the value referred to by a reference is called dereferencing
it. References are fundamental to constructing many data structures (such as
linked lists) and in exchanging information between different parts of a
program.

Pointer:
In computer science, a pointer is a programming language data type whose value
refers directly to (or "points to") another value stored elsewhere in the
computer memory using its address. Obtaining the value to which a pointer
refers is called dereferencing the pointer. A pointer is a simple
implementation of the general reference data type (although it is quite
different from the facility referred to as a reference in C++).

====================================================================
   * Call-by-value.  Pass the r-value of A[j].
   * Call-by-reference.  Pass the l-value of A[j].
   * Call-by-name.  Pass the text of A[j] itself, avoiding "name clashes."

================================= C =================================
pass by value semantics

---------------------------------------------------------------------------
int a = 5;
int *money = NULL;
 
money = &a;

*money = 8;

malloc(int variable)
free(pointer)
---------------------------------------------------------------------------

---------------------------------------------------------------------------
 void alter(int *n) {
     *n = 120;
 }
 
 void func(void) {
     int x = 24; 
     alter(&x);
 }
---------------------------------------------------------------------------

---------------------------------------------------------------------------
int *ptr = malloc(sizeof (int));
free(ptr);
*ptr = 0;
---------------------------------------------------------------------------

---------------------------------------------------------------------------
int array[5];      
int *ptr = array;  
ptr[0] = 1;        
*(array + 1) = 2;  
---------------------------------------------------------------------------

---------------------------------------------------------------------------
================================= C++ ================================= 
---------------------------------------------------------------------------

---------------------------------------------------------------------------
int& preinc(int& x) { ++x; return x; }
preinc(y) = 5; 
---------------------------------------------------------------------------

---------------------------------------------------------------------------
void swap ( int lhs, int rhs) {
    int temp = lhs;
    int lhs = rhs;
    int rhs = lhs;
}

void swap ( int& lhs, int& rhs);}
    int temp = lhs;
    int lhs = rhs;
    int rhs = lhs;
}
---------------------------------------------------------------------------

=================================  Java ===================================
---------------------------------------------------------------------------

public void swap(int var1, int var2)
{
  int temp = var1;
  var1 = var2;
  var2 = temp;
}

---------------------------------------------------------------------------

public void swap(Integer var1, Integer var2)
{
  Integer temp = var1;
  var1 = var2;
  var2 = temp;
}

---------------------------------------------------------------------------

public void tricky(Point arg1, Point arg2)
{
  arg1.x = 100;
  arg1.y = 100;
  Point temp = arg1;
  arg1 = arg2;
  arg2 = temp;
}

public static void main(String [] args)
{
  Point pnt1 = new Point(0,0);
  Point pnt2 = new Point(0,0);
  System.out.println("X: " + pnt1.x + " Y: " +pnt1.y); 
  System.out.println("X: " + pnt2.x + " Y: " +pnt2.y);
  System.out.println(" ");
  tricky(pnt1,pnt2);
  System.out.println("X: " + pnt1.x + " Y:" + pnt1.y); 
  System.out.println("X: " + pnt2.x + " Y: " +pnt2.y);  
}


---------------------------------------------------------------------------
=============================  PYTHON  ====================================
---------------------------------------------------------------------------

def foobar(a):
   a = 0 

a = 1 
foobar(a) 
a = [1, 2, 3] 
foobar(a) 
>def foobar(a):
>   a *= 2 

a = 1 
foobar(a) 
a = [1, 2, 3] 
foobar(a)