WEBVTT 00:00.760 --> 00:08.290 In general function names have the same rules for variables, so they must begin with a letter or an 00:08.290 --> 00:13.800 underscore and cannot contain spaces or other punctuation characters here. 00:13.810 --> 00:17.410 So now I'm going to write some functions. 00:18.580 --> 00:27.550 Integer My function here, an integer like my function. 00:29.360 --> 00:33.070 And when we do the integer it here. 00:34.310 --> 00:45.200 This is the illegal and the compiler compiler will or will not compile here will not compile. 00:46.470 --> 00:46.890 Here. 00:48.390 --> 00:49.200 And. 00:50.830 --> 00:58.570 Uh, as I said earlier, they must begin with a letter or an underscore character and cannot contain 00:58.570 --> 01:05.470 spaces, as you can see here or other punctuation characters, for example, like dot comma here, they 01:05.470 --> 01:09.360 cannot contain any punctuation characters for. 01:09.370 --> 01:16.360 So following the general principle of Self-documenting code, you should name the function according 01:16.390 --> 01:18.580 to what it does. 01:18.580 --> 01:25.420 So there is one exception, and these are the special functions used to provide overloads for operators, 01:25.570 --> 01:27.880 which is mostly punctuation symbols. 01:27.880 --> 01:36.310 So these functions have a name in the form here, for example, the multi-year where the. 01:37.600 --> 01:43.300 Mold is like describing the function which will will multiply the two values one by one. 01:43.300 --> 01:46.690 So operators are one example of overloading here. 01:46.690 --> 01:53.950 So you can overload any function that is use the same name, but provide implementations with different 01:53.950 --> 01:57.120 parameter types or different parameter numbers. 01:57.130 --> 02:01.210 We can make it like that, for example, integer multi-year. 02:01.240 --> 02:03.020 We can make multiply. 02:03.220 --> 02:10.390 We we can multiply three numbers one by one here, for example, l h s integer r h s. 02:10.420 --> 02:15.040 If you make it like that or just make it integer, for example. 02:16.860 --> 02:19.100 Actually they will return the same value. 02:19.110 --> 02:22.470 This is just a different writing in C plus plus here. 02:22.470 --> 02:26.190 As you can see, we're going to get error because they are the two same function. 02:26.190 --> 02:30.600 As you can see the redefinition of multi year, multi, multi year. 02:30.600 --> 02:38.760 So if we make add another parameter integer x x, we're going to make the overloading function here 02:38.760 --> 02:47.460 and we're going to return the return, the multiply by an error and multiply in multiply it by the X 02:47.460 --> 02:49.380 age s here. 02:49.380 --> 02:55.560 And if you make it like that as standard C out. 02:57.040 --> 02:59.620 See out here and here. 02:59.620 --> 03:01.390 The most we're going to multiply. 03:01.390 --> 03:08.400 We're going to call this here 8 or 910. 03:08.410 --> 03:18.820 So in this case, uh, the multiply function will, uh, this code here, this code will call this function 03:18.820 --> 03:22.900 because this takes parameters and we gave this function two parameters. 03:22.900 --> 03:29.830 If we make it like that, uh, this is going to call the, uh, the third function. 03:29.920 --> 03:35.350 The second function here that we have three parameters and we are calling this function. 03:35.350 --> 03:39.310 So, and this named the function overloading here. 03:40.070 --> 03:45.050 As you can see here, we multiplied the three numbers one by one here. 03:45.050 --> 03:45.710 So. 03:47.140 --> 03:48.850 Uh, we have function parameters. 03:48.850 --> 03:53.500 The function here, they may not have any parameters like this here. 03:53.500 --> 03:58.750 For example, we can create a function with that parameters like this. 03:58.750 --> 04:05.170 But they let's return create without parameters, but we'll have the return value. 04:05.170 --> 04:14.740 So in which case the case is the function is the fate defined with a pair of empty parentheses. 04:15.130 --> 04:17.110 Uh, like this here, for example. 04:17.110 --> 04:18.370 So a function. 04:18.580 --> 04:26.170 The function definition must give the type and name of the parentheses parameters between parentheses 04:26.170 --> 04:27.070 like this here. 04:27.070 --> 04:28.090 So. 04:29.280 --> 04:34.500 And, uh, in many cases the functions will have a fixed number of parameters. 04:34.500 --> 04:37.800 But you can write functions with a variable number of parameters. 04:37.800 --> 04:42.610 So you can also define functions with the default values or some of the parentheses. 04:42.630 --> 04:45.150 So some of the parameters. 04:45.150 --> 04:52.110 So in effect a providing a function that overloads itself on the number of parameters parameters passed 04:52.110 --> 04:53.550 to the function. 04:53.550 --> 05:00.090 So variable argument list and default arguments will be covered later in this course. 05:00.090 --> 05:07.950 Here we can also make the make the specify the exceptions in C plus plus function here. 05:07.950 --> 05:14.010 The functions also can be marked to indicate whether they will throw an exception. 05:14.010 --> 05:18.570 So more details about exceptions will be given in next lecture. 05:18.570 --> 05:22.410 But there are two syntaxes you need to be aware of. 05:22.440 --> 05:29.170 So earlier versions of C plus plus allowed you to use the trough specifier. 05:30.350 --> 05:34.320 Uh, specified on the function in three ways. 05:35.210 --> 05:43.190 Firstly, you provide a comma separated list of types of the exceptions that may be thrown by code in 05:43.190 --> 05:44.150 the function here. 05:44.870 --> 05:49.040 The second you can provide an ellipsis like this. 05:49.520 --> 05:50.240 Here. 05:53.000 --> 05:58.580 Lapses or which means that the function may throw an exception. 05:58.580 --> 06:06.050 And thirdly, you can provide an empty pair of parentheses, which means that the function will not 06:06.050 --> 06:07.220 throw an exception. 06:07.220 --> 06:08.840 So the syntax here. 06:09.110 --> 06:13.700 Throwing exceptions to exceptions looks like this. 06:13.700 --> 06:19.220 For example, throw we're going to specify the exceptions. 06:19.220 --> 06:23.930 For example overflow overflow error and. 06:25.320 --> 06:25.770 Do. 06:25.800 --> 06:30.930 We're going to make, for example, do something which potentially. 06:32.550 --> 06:34.980 May overflow flow. 06:35.190 --> 06:40.290 So the trough specifier has been deprecated in C plus plus 11. 06:40.290 --> 06:47.430 As you can see, the compiler will say the dynamic exception specifier, uh, overflow error is deprecated. 06:47.430 --> 06:50.700 Consider using noexcept files instead. 06:50.700 --> 06:58.020 Here we can change ignore accept files so it throws specifier has been deprecated in C plus. 06:58.020 --> 07:03.660 Plus is largely because the ability to indicate that the type of function was not useful. 07:03.660 --> 07:10.260 So however, the version of throw that indicates that no exception will be thrown was found to be useful 07:10.290 --> 07:18.690 because it enables the compiler to optimize code by providing no code infrastructure to handle exceptions 07:18.690 --> 07:19.950 here, exceptions here. 07:19.950 --> 07:29.160 So the C plus plus 11 retains this behavior with no accept specifier and the no accept specifier. 07:29.160 --> 07:34.930 Here we can delete this false here and add with no accept specifier. 07:34.930 --> 07:36.220 We're going to check. 07:37.280 --> 07:44.720 Check the parameter and handle overflow appropriately. 07:47.380 --> 07:48.010 Here.