Pointer Kung Foo (c++)

[SpookyEddy]

I am learning c++, however I am used to higher level languages with no messing around with memory managment and pointers etc. I have got to grips with the basic idea of pointers, the whole "variable that contains a memory address" deal and referencing/dereferencing etc.

That said, pointers are something I never normaly use as they don't exist in most of the languages I use (Ruby, perl, vbscript etc). So.. I want you to sell me pointers. What are the cool (and preferably fairly simple) things I can do with pointers just to mess around and get a better understanding?

Thanks

ed

[Jüš† ä gü¥]

bool function(){
int number;
int* numptr;
numptr=&number;
*numptr=5;
return (number==5);
}


You will always get "true"

Actually, understand that example and you'll pretty much have pointers under your belt.

[jkrohn]

Pointers do exist in Perl as references though they do not allow direct memory manipulation as c++ does.

What are the uses? Plenty. Mainly I find them most useful in creation of data structures. Trees, lists, graphs, etc.

Such things are either not possible or much more difficult in other languages. (Recursive link lists anyone ?)

Jkrohn

[JohnRoboto]

Java (which does not use pointers) contains trees, lists, graphs, etc.. built directly in the native API.

IMHO, pointers are excessively confusing and can be dangerous and I personally haven't found any direct advantage to using them. Perhaps someone can inform me?

[SpookyEddy]

Actually, understand that example and you'll pretty much have pointers under your belt.

While I understand that example fine, it seems about as simple as pointers get. What I was looking for was common uses of pointers really. Thanks anyway though.

Thanks for the ideas jkrohn, the stuff you said on irc was interesting.

Regards

ed

[KraM]

I can think of a couple of uses...

If you need a function to return more than 1 value or an array:

int aFunction(int input, int *return2) {
  int *b;
  b = malloc(input * sizeof(int));
  // put something in array
  b[0] = 10;
  b[input - 1] = 200;
  *return2 = b;
  return anotherValue;
}

scanf uses pointers to put read in values into whatever memory locations its supplied arguments are pointing to.

You need it for manipulating specific memory locations. I would suppose device drivers need this facility:

*((int*)0x200000) = 0x55;

This would put 0x55 in memory location 0x200000.

This is C though, I don't know if it would work in C++.