Ex: What is the difference between 'void func(int *var)' and 'void
func(int **var)'? What about 'int &var'?
The same question stands for return types, as well as arguments. What
does 'int& func(int var)' mean, as compared to 'int* func(int var)'?
And in arguments, how does 'y = func(*x)' differ from 'y = func(&x)'?
(1)
void func (int *var)
here int *var is a pointer to integer, ie it can point to
an array or any buffer that should be handled with integer pointer
arithmetic. In simple terms , var holds the address of the respective
**actual parameter.**
eg: int arr[10];
func(arr);
int a = 33;
func(&a);
Here, &a means we are explicitly passing address of the the variable 'a'.
(2)
int m = 0;
int &var = m;
Here var means reference, ie it another alias name for variable 'm' ,
so any change 'var' makes will change the contents of variable 'm'.
var = 2; /* will change the actual contents of 'm' */
This simple example will not make sense , unless you understand the context.
Reference are usually use to pass parameter to function, so that changes made by
the function to the passed variable is visible at the caller.
int swap(int &m, int &n) {
tmp = m;
m = n;
n = tmp;
}
void main( void ) {
int x = 1, y = 2;
swap(x, y);
/* x = 2, y =1 */
}
(3)
'int& func(int var)' mean, as compared to 'int* func(int var)'?
int& func(int var) means the function returns a reference;
int* func(int var) means the function returns a pointer / address;
Both of the them has its context;
int& setNext() {
return next;
}
setNext() = previous;
where as
int* setNext() {
return &next;
}
int *inptr;
inptr = setNext();
*inptr = previous;
In the previous two lines,
int *inptr <- integer pointer declaration;
*inptr <- means we are accessing contents of the address pointed by inptr;
ie we are actually referring to 'next' variable.
The actual use is context specific. It can't be generalized.
(4)
how does 'y = func(*x)' differ from 'y = func(&x)'?
y = func(&x) is already explained.
y = func(*x) , well i'm not sure if you actually meant *x.
int swap(int *m, int *n) {
tmp = *m;
*m = *n;
*n = tmp;
}
