WEBVTT 00:00.150 --> 00:01.050 After variables. 00:01.050 --> 00:02.940 Let's see what functions are. 00:02.940 --> 00:08.280 And as we did for valuables, let's first understand why you need functions. 00:08.280 --> 00:09.900 And I'm going to go quite quick here. 00:09.900 --> 00:10.100 Okay? 00:10.110 --> 00:16.620 The goal is to give you an overview of functions, not to go into much details about everything you 00:16.620 --> 00:22.470 can do about functions, so you will learn more about functions as you progress in the course through 00:22.470 --> 00:25.440 how the different activities and practice exercises. 00:25.710 --> 00:29.610 So if it doesn't make complete sense for now, well, don't worry too much. 00:29.610 --> 00:31.710 It will by the end of the course. 00:31.710 --> 00:32.940 So what do we have here? 00:32.940 --> 00:33.150 What? 00:33.150 --> 00:35.430 I have created two variables here. 00:35.430 --> 00:36.720 You can see number one. 00:36.720 --> 00:41.910 And number two, those variables are integer numbers three and five. 00:41.910 --> 00:48.300 And what I do in the void setup is I just well, I just create a new variable A that is the double of 00:48.300 --> 00:51.800 number one, and then B, that is the double of number two. 00:51.810 --> 00:55.560 So let's say that what you want to do is simply to multiply the number by two. 00:55.560 --> 00:59.280 And so every time you're going to need to do the variable multiplied by two. 00:59.330 --> 01:05.190 Thing is this would be very inconvenient to always need to repeat the same code every time you need 01:05.190 --> 01:06.810 to use this functionality. 01:06.810 --> 01:11.670 And here it's a very small functionality, but the functionality can be much bigger with many lines 01:11.670 --> 01:12.240 of code. 01:12.660 --> 01:15.390 So what we need here is a function. 01:15.840 --> 01:22.530 A function is a reusable block of code that you can call from different parts of your program. 01:22.530 --> 01:24.840 And let's just create one to see what it is. 01:24.840 --> 01:26.730 So I'm just going to create a function here. 01:26.730 --> 01:31.290 Actually, void setup is already a function and void loop is a function. 01:31.740 --> 01:38.850 So let's create a new one here on top and let's call it double number like this, because we want to 01:38.850 --> 01:45.300 double a number and I'm going to make sure that I don't add any spaces for any new world. 01:45.300 --> 01:48.840 I just added new uppercase and you can see that at the beginning of the function. 01:48.840 --> 01:49.920 So that will be the name. 01:49.920 --> 01:54.780 But at the beginning of the function, we have something and we need to give the data type that we want 01:54.780 --> 02:01.590 to return because the function will accept some parameters as an input and we'll return something as 02:01.590 --> 02:02.610 an output. 02:02.710 --> 02:06.150 And so here I'm just going to put INT and then space double number. 02:06.150 --> 02:10.230 That means that this function will return an integer number. 02:10.230 --> 02:16.260 So I put the data type the name, and then I open and close the parentheses and I have the definition 02:16.260 --> 02:17.070 of my function. 02:17.070 --> 02:19.720 You can see just like the void set up and the void loop. 02:19.740 --> 02:24.840 Now what I can also do is when I have a function, as I told you, we can give it an input. 02:24.840 --> 02:30.780 And so the input here, I'm just going to put int number, which means that the function can receive 02:30.780 --> 02:36.060 an integer value here that's going to be named number inside the function. 02:36.060 --> 02:41.610 And once I have this, I can just go back to a new line and open and close curly brackets. 02:41.820 --> 02:42.050 Okay. 02:42.060 --> 02:44.970 Very similar to what we did here with void, setup and void. 02:45.120 --> 02:48.900 But in this case you can see I have INT and I also have one parameter. 02:48.900 --> 02:51.600 You could have as many parameters as you want. 02:51.630 --> 02:54.180 You just separate them with a comma. 02:54.570 --> 02:58.110 But let's just keep things simple for now with just one parameter. 02:58.200 --> 03:01.530 So this what is this function doing? 03:01.530 --> 03:06.210 Well, this function will need to actually multiply the number here by two. 03:06.300 --> 03:09.360 So let's just create a variable. 03:09.360 --> 03:15.030 INT result, for example, is equal to number multiplied by two. 03:15.840 --> 03:17.760 The number is the variable. 03:17.760 --> 03:21.750 As you can see that we get here in the parameter of the function. 03:21.750 --> 03:23.430 So that's what we do in the function. 03:23.430 --> 03:26.340 And then there is a keyword that you need to use in a function. 03:26.340 --> 03:31.350 It's called return can see turns green return result. 03:31.440 --> 03:33.240 So what do I return? 03:33.240 --> 03:37.800 I return this variable and this variable is an integer number. 03:37.800 --> 03:40.200 So that match is the type that I want to return. 03:40.440 --> 03:42.240 So now I have this block of code. 03:42.240 --> 03:48.390 You can see this block of code that's going to take as an input a number here, an integer number, 03:48.390 --> 03:51.150 and that's going to return another integer. 03:51.150 --> 03:57.960 But you can see this time the returned number is the double of the number that we pass as an input. 03:57.960 --> 04:01.410 And so once I have created a function, I can actually use it. 04:01.410 --> 04:08.280 And so here, instead of doing number one multiplied by two, I can just what we call calling the function. 04:08.280 --> 04:10.470 Actually, I can call the function. 04:10.470 --> 04:15.990 So double number and I pass number one. 04:16.920 --> 04:23.670 Double number, I call this function and I pass what I pass the number one variable here that I will 04:23.670 --> 04:26.280 pass to the input of the function. 04:26.280 --> 04:27.870 And so the number one will go here. 04:28.380 --> 04:34.560 It will be multiplied by two, and then we return the result, which means that it will go back here 04:34.560 --> 04:41.430 and then a will be equal to the result of this function, which is the double of the number. 04:41.730 --> 04:50.820 And I can do the same thing here, double number with number two, for example, I can give a different 04:50.820 --> 04:51.810 number every time. 04:51.810 --> 04:57.150 Okay, so that's a reusable block of code that I can use with a different number every time. 04:57.150 --> 04:57.600 Great. 04:57.600 --> 04:59.850 And that's a first example of a. 04:59.870 --> 05:03.680 Function and well, you can combine functions as much as you want. 05:03.680 --> 05:08.300 For example, you could call a function inside another function, and that's what we are going to do 05:08.300 --> 05:08.690 here. 05:08.690 --> 05:13.790 I'm going to create a function and I'm going to name it Void, and I'm going to explain to you void 05:13.790 --> 05:20.420 print double number and this one gets also int number. 05:20.660 --> 05:21.620 So what is this? 05:21.620 --> 05:24.890 Well, you can see that with a function you need to return data type. 05:24.890 --> 05:31.700 So you need to return, for example, an int or a float number or any other kind of data. 05:31.700 --> 05:36.260 But if you put void, void means that you will not return anything. 05:36.260 --> 05:39.530 And you can see that's actually what's happening in the void setup. 05:39.530 --> 05:45.560 This is a function and the void loop also is a function, but you don't have any return keyword because 05:45.560 --> 05:46.370 this is void. 05:46.790 --> 05:49.550 So we don't have any return keyword and that's what we do here. 05:49.550 --> 05:55.700 What we want to do is just to print the double of the number that we get from the parameter. 05:55.940 --> 06:00.710 So I put the void and then I put my opening and closing curly brackets. 06:00.710 --> 06:05.540 And what I can do here, let's say I want to so I want to print the double of this number. 06:05.540 --> 06:12.650 But instead of doing number multiplied by two, I can just call this function so I could do serial dot 06:13.040 --> 06:16.640 print ln to print something. 06:16.640 --> 06:23.960 And what I can print is I can just do double number and I pass the number that I receive. 06:23.960 --> 06:28.100 I pass it here and I close all the parentheses. 06:29.000 --> 06:35.090 So what's going to happen here is that if I call this function from here, let's say call it here, 06:35.180 --> 06:44.060 print double number with number one, what's going to happen is so we have created number one here and 06:44.060 --> 06:48.710 then we call the function named print double number with number one. 06:48.710 --> 06:49.910 So we go here. 06:51.140 --> 06:53.120 The number one is going to be passed here. 06:53.120 --> 06:58.220 So the int number in this function is going to become the value of number one. 06:58.220 --> 06:59.240 So it's going to be three. 06:59.750 --> 07:00.920 So here we have three. 07:01.430 --> 07:06.080 And then what we do is we do select println with double number. 07:06.080 --> 07:08.720 So here we are calling another function. 07:08.720 --> 07:12.110 So you see from one function we call another function. 07:12.350 --> 07:16.700 And so I call the double number and I pass what I get here as an input. 07:16.700 --> 07:20.060 I pass it here as an input for this function. 07:20.060 --> 07:23.330 So you can see I pass the values from function to function. 07:23.330 --> 07:29.000 And then this function is going to compute the double of the number, return the double of the number. 07:29.000 --> 07:30.430 So return the result. 07:30.440 --> 07:36.770 And so basically this here is going to be evaluated to the result of the function. 07:37.310 --> 07:39.470 So this will become the double of the number. 07:39.470 --> 07:42.050 And then what we do is we print the double of the number. 07:42.050 --> 07:42.680 All right? 07:42.770 --> 07:50.570 And so we can we can actually call it once I can call it twice with different numbers, etc., Actually, 07:50.570 --> 07:53.490 if we want to test, I would also need to initialize sales. 07:53.500 --> 07:55.190 So begin. 07:56.150 --> 07:57.980 Let's put this. 07:58.930 --> 07:59.770 Moderate. 08:00.840 --> 08:03.150 And let's actually run this. 08:04.990 --> 08:06.730 Lets name it functions. 08:07.790 --> 08:08.210 Okay. 08:08.330 --> 08:09.170 Don't uploading. 08:09.170 --> 08:14.780 If I open the sale monitor, you will see that we have six and ten. 08:15.260 --> 08:18.230 So six is the double of the number one. 08:18.230 --> 08:22.040 Three and ten is the double of the number two five here. 08:22.550 --> 08:24.680 So what I do, I just print double number. 08:24.680 --> 08:31.340 So I pass the three is going to go here to double number is going to go here is going to be return and 08:31.340 --> 08:32.120 we print it here. 08:32.480 --> 08:35.000 And then number two is going to be five. 08:35.000 --> 08:37.670 So we call this function with five. 08:37.910 --> 08:42.710 It goes here on line eight and then we call the one number on line two. 08:43.340 --> 08:49.460 So the number five is passed until here and then we reach on ten and then here we can print ten. 08:49.640 --> 08:56.540 And one thing we can maybe do also here as an improvement is that, well, in the double number function, 08:56.540 --> 09:00.980 what we do is we create a viable that we just return. 09:01.220 --> 09:05.880 So we don't use this variable for anything else than to return it. 09:05.900 --> 09:12.500 So instead of just creating that, I can just actually do return number multiplied by two. 09:13.730 --> 09:19.340 So if it's the last thing to do is you don't need to use the variable that you create, then you just 09:19.340 --> 09:22.580 can return whatever that you compute here directly. 09:22.580 --> 09:23.940 And this is going to work the same. 09:23.960 --> 09:24.350 All right. 09:24.350 --> 09:27.350 So that was a very quick introduction about functions. 09:27.350 --> 09:32.180 I know this is a quite complex topic when you begin, but don't be afraid if you don't understand everything, 09:32.180 --> 09:37.970 it will all make sense while we go through how the course with all of the different exercises. 09:37.970 --> 09:38.160 Okay. 09:38.210 --> 09:43.610 And later on, you can come back to this lesson and eventually it will make more sense.