WEBVTT 00:01.040 --> 00:11.030 Be some use for the int pointer pointer in the last lecture which we use for dynamically allocating 00:11.280 --> 00:13.310 it to the array. 00:13.970 --> 00:21.530 But it was it really me well it really means a pointer to a pointer and so a pointer that points to 00:21.680 --> 00:22.730 another point. 00:22.730 --> 00:29.540 In other words if you call in our pointers discussion I mentioned that you couldn't modify where pointer 00:29.540 --> 00:30.170 points to. 00:30.170 --> 00:37.890 If you pass it to a function the original pointer will be completely unaffected. 00:38.380 --> 00:47.710 Well if we want to change the pointer itself or the value itself then we can pass it by pointer pointer 00:47.710 --> 00:48.240 instead. 00:48.280 --> 00:52.470 So let's take a look at the example I have here. 00:52.540 --> 01:00.230 So what this program really does is all it does is create a pointer. 01:00.430 --> 01:05.010 So you put 0.06 that owns and is going to own some memory. 01:05.080 --> 01:11.410 So you just create a new int array of a bunch of. 01:11.890 --> 01:13.250 It's OK Max. 01:13.280 --> 01:18.200 So in this case 10 then I will print out the length. 01:18.200 --> 01:24.890 So currently It's 10 on the first iteration and then I will just fill the array with some values and 01:24.890 --> 01:27.290 then print those out. 01:27.530 --> 01:28.020 OK. 01:28.060 --> 01:30.470 So that's all this does. 01:30.470 --> 01:37.960 And after that I will ask the user for some more or a new link. 01:38.270 --> 01:48.460 And if that link is greater than zero I will actually resize the array itself using this function. 01:48.470 --> 01:52.660 So let's just run this and see what happens. 01:53.600 --> 01:56.100 So I like this now 10. 01:56.150 --> 01:58.390 That's what you'd expect at the start. 01:58.400 --> 02:00.260 And then say I ran it. 02:00.260 --> 02:06.710 Or put a new link to be 20 and it will fill the array with 20 values. 02:06.760 --> 02:11.060 Ok so now the array is actually 20 instead of 10. 02:12.040 --> 02:18.190 And I said you know 9 it's only 9 now. 02:18.770 --> 02:23.270 And if I said 0 then it quits OK. 02:23.530 --> 02:24.790 That's greater than zero. 02:24.830 --> 02:26.130 For this to work. 02:26.420 --> 02:28.840 And of course I do it after. 02:28.850 --> 02:30.980 So how did this work. 02:30.980 --> 02:31.450 Right. 02:31.700 --> 02:32.370 Actually. 02:32.450 --> 02:39.740 So what this does is actually changes where this points to changes the address that this points to. 02:39.800 --> 02:43.040 So we did this using a pointer pointer 02:45.280 --> 02:46.320 arguments. 02:46.480 --> 02:53.210 So notice that this resize takes it by pointer a pointer and not just one pointer. 02:53.290 --> 02:56.440 It's not it's not this it should be this way. 02:56.500 --> 03:04.870 So and you'll notice if you when we actually use it down here we're actually passing the address of 03:05.050 --> 03:06.730 our pointer. 03:07.050 --> 03:14.380 OK so that's what really that means so this pointer pointer takes an address of a pointer. 03:14.440 --> 03:19.080 So that's what this does and that's why this is how it is here. 03:21.140 --> 03:28.970 So the resize function again it takes a point your pointer will check to see if any pointers. 03:28.980 --> 03:29.560 No. 03:30.170 --> 03:40.070 If it isn't then it actually deletes the memory pointed to by the original pointer so Notice I'm using 03:40.070 --> 03:50.530 the dereference operator here because I need to get the original pointer value original pointer address. 03:50.570 --> 03:54.630 OK that's what this says and I actually delete it. 03:55.070 --> 04:02.700 And then here I'll actually sent the original pointer right this is the original pointer and with the 04:02.710 --> 04:11.040 error and the dereference operator start of it and I'll actually set it to some new size. 04:11.630 --> 04:17.790 So I actually like i actually change where the original pointer points to. 04:17.790 --> 04:18.620 In other words. 04:18.660 --> 04:23.870 And how much point and the length of the array that it gets. 04:24.090 --> 04:29.050 OK so that's kind of how this works. 04:29.070 --> 04:34.800 So notice I can't do this so I'm deleting where 04:37.960 --> 04:42.160 I delete that dereference like it'll start it'll mess up. 04:42.170 --> 04:52.030 So the saying pointer being freed was not allocated meaning this double pointer never had anything to 04:52.030 --> 05:02.270 begin OK it's only the original pointer that had something or pointed to some memory. 05:02.440 --> 05:10.560 So that's all I really want to say about these pointer pointers we will actually use them in the battleship 05:10.560 --> 05:15.900 project but not in terms of dynamic memory of using them in a different way. 05:15.900 --> 05:26.470 Actually in the next lecture I want to do want to go over some one more use of pointers you might find 05:26.530 --> 05:27.310 kind of interesting.