WEBVTT 00:00.780 --> 00:02.280 So far in this course. 00:02.310 --> 00:07.090 Initializer list have been treated as a kind of C plus plus 11 construct. 00:07.140 --> 00:09.150 And a bit like the bulletin arrays. 00:09.330 --> 00:17.610 So, in fact, when you use the initializer list syntax using the braces here, the compiler actually 00:17.610 --> 00:23.410 creates an instance of the templated initialize list class here. 00:23.430 --> 00:30.180 So if an initializer list is used to initialize another type, for example, in this case the vector 00:30.180 --> 00:30.840 here. 00:33.920 --> 00:43.990 Uh, then the compiler creates an initialize list object and with the given values between the braces 00:43.990 --> 00:51.190 here, so and the container object is initializing the initializer list iterator. 00:51.190 --> 00:59.080 So this ability to create an initialized list object from a braced initializer list can be used to give 00:59.080 --> 01:01.300 a function a variable number of parameters. 01:01.300 --> 01:03.430 So I'll beat all of the parameters. 01:03.430 --> 01:06.160 Must be the same type in this case here. 01:06.160 --> 01:11.980 So in order to use this initializer list, we have to firstly include the initializer. 01:13.080 --> 01:14.400 Initializer list. 01:15.000 --> 01:16.290 Header file here. 01:16.290 --> 01:23.190 And then we're going to create a new function named sum and. 01:23.970 --> 01:25.980 But you can return the integer here. 01:26.130 --> 01:28.380 Sum and initial. 01:34.490 --> 01:36.290 List here and. 01:37.170 --> 01:37.890 Then. 01:42.370 --> 01:48.040 This initializer list will take the integer values here and make it values. 01:48.580 --> 01:52.670 So this sum here takes the parameter values. 01:52.690 --> 01:58.300 This will take one parameter and the type of initializer list integer here. 01:58.300 --> 02:03.940 So which here integer sum equals zero here, for example. 02:03.940 --> 02:07.900 And we're going to create a for loop integer values. 02:08.440 --> 02:11.590 We're going to iterate throughout this parameter. 02:12.630 --> 02:13.320 Values. 02:13.320 --> 02:16.050 And with this for loop. 02:16.080 --> 02:28.050 We're going to use this as the we're going to some increment, some by one at every or some by e here 02:28.080 --> 02:30.300 at every iterating here. 02:31.160 --> 02:35.000 And we're going to after this, we're going to return the. 02:35.960 --> 02:37.970 Add some integer here. 02:38.150 --> 02:44.000 So in the main function we're going to create, we're going to make actually the main function is going 02:44.000 --> 02:50.960 to just print something and call this some, uh, function here that we created here. 02:51.350 --> 02:53.210 So C out. 02:54.960 --> 02:55.650 Some. 02:57.270 --> 02:59.040 Here and. 02:59.850 --> 03:00.630 End line. 03:00.840 --> 03:06.990 Firstly, we're going to call just an empty sum and see out sum. 03:07.200 --> 03:09.450 Here we're going to pass the values here. 03:09.450 --> 03:16.500 In this case, we're going to pass the negative values starting from six minus six, negative six here. 03:17.910 --> 03:22.770 Five, four, three, two. 03:23.870 --> 03:27.410 One and here and line. 03:28.820 --> 03:29.780 So. 03:30.660 --> 03:31.680 C out. 03:32.130 --> 03:33.240 C out. 03:33.270 --> 03:33.840 Some. 03:33.840 --> 03:41.400 And this case we're going to make give it a ten, 20, 30 and end line here. 03:41.400 --> 03:50.790 So in this case, we're going to get the if we pass the NON-OBJECT to this some function, we're going 03:50.790 --> 03:51.720 to get a zero. 03:51.720 --> 03:55.680 In this case, we're going to get the -2021. 03:55.680 --> 04:02.910 And in this case, we going to get the 16, as you can see here. 04:02.910 --> 04:11.400 And the sum function here has a single parameter initializer list integer here, which can only be initialized 04:11.400 --> 04:14.730 with the list of integers here. 04:14.730 --> 04:21.180 So the initializer list class has a very few functions because it only exists to give access to the 04:21.180 --> 04:23.340 values in the brace list here. 04:23.340 --> 04:32.860 So most significantly, it implements a size function that returns the number of items in the list here. 04:32.860 --> 04:35.470 So you can use values that size. 04:35.500 --> 04:40.780 As you can see, this will return the number of items in the list. 04:41.200 --> 04:42.160 Let me mention it. 04:42.160 --> 04:44.860 So when you download this code, you're going to see. 04:45.570 --> 04:50.760 Returns, number of items in the list. 04:51.330 --> 04:52.650 So here. 04:53.710 --> 04:58.110 And size function returns the number of items in the list. 04:58.120 --> 04:59.200 So. 05:00.660 --> 05:07.680 And the begin and end functions in return pointer to the first item in the list and to the position 05:07.680 --> 05:09.060 after the last item. 05:09.060 --> 05:16.950 So these two functions are needed to give iterator access to the list and it enables you to use the 05:16.950 --> 05:20.730 object with with the range for loop here. 05:20.730 --> 05:26.220 So as you can see here, we when we compile the code, we're going to get the zero -20. 05:26.220 --> 05:29.550 Why 21 and 60 here? 05:29.820 --> 05:35.790 So in this example, the main function here calls this function three times the sum function, three 05:35.790 --> 05:40.980 times each time with the priest initializer list here, as you can see here. 05:41.100 --> 05:47.670 So and the function will return the sum of some of the items in the list here. 05:47.670 --> 05:56.610 And as you can see, it, will the sum here multiply or will some of the numbers in the list? 05:56.610 --> 06:02.830 So clearly, this technique means that the each item in the variable parameter list has to be the same 06:02.830 --> 06:09.130 type or type that can in can be converted to a specify specified type. 06:09.130 --> 06:14.320 So you will have the same result if the parameter had been vector. 06:14.320 --> 06:21.880 And the difference is that the initializer initializer list parameter requires the list initialization 06:21.880 --> 06:22.210 here. 06:22.210 --> 06:26.950 So if we make it like this two point make, give it the 2.1. 06:26.950 --> 06:33.010 As you can see here, we are going to get error because the initializer list can only you can just only 06:33.010 --> 06:38.110 pass the values that has the same type as this parameter here.