WEBVTT 00:00.110 --> 00:02.690 Almost done with the programming basics. 00:02.720 --> 00:06.200 Now let's look at loops. 00:06.200 --> 00:08.750 And again let's first understand why. 00:08.840 --> 00:12.590 Here is a basic example that I'm going to run. 00:13.560 --> 00:14.880 So loops. 00:15.510 --> 00:18.360 And as you can see, this is quite stupid. 00:18.360 --> 00:24.150 But we want to print hello ten times and you can see hello ten times. 00:24.150 --> 00:28.440 And here it's stupid because we just need to write println. 00:28.440 --> 00:29.910 Hello ten times. 00:29.910 --> 00:33.270 What happens if I need to print hello a thousand times? 00:33.270 --> 00:39.930 Well, whenever you need to repeat something more than two times, this would be best to use a loop. 00:39.930 --> 00:42.990 So here I'm going to show you two kinds of loop. 00:42.990 --> 00:45.330 The for loop and the while loop. 00:45.330 --> 00:48.240 Let's first see how to use the for loop. 00:48.240 --> 00:51.870 So I'm going to just remove all of that. 00:52.200 --> 00:53.910 And let's use a for loop. 00:54.180 --> 00:56.820 So you can start with four. 00:56.850 --> 00:58.950 You can see the keyword for in green. 00:58.950 --> 01:01.080 Then you open the parenthesis okay. 01:01.080 --> 01:04.110 And then I'm going to write it and explain it just after. 01:04.110 --> 01:07.650 So int I is equal to zero. 01:08.760 --> 01:12.030 And then semicolon I lower than ten. 01:12.030 --> 01:20.220 Semicolon I plus plus close the parentheses I open curly brackets, I press enter. 01:20.220 --> 01:26.910 This automatically closes the curly brackets block and adds a two space indentation. 01:26.910 --> 01:30.900 And then I can just put this right here. 01:32.770 --> 01:33.100 Right. 01:33.100 --> 01:35.410 And this let's let's run this. 01:35.410 --> 01:40.180 This will do the exact same thing, but with just three lines of code. 01:40.540 --> 01:43.120 Okay, you can see hello ten times. 01:43.420 --> 01:47.500 So here a little bit more because we already had I'm going to clear the output. 01:50.500 --> 01:51.430 Okay ten times. 01:51.430 --> 01:55.210 We have already had data from the previous run on the serial monitor. 01:55.510 --> 01:55.930 So. 01:55.930 --> 01:57.400 Well, how to create a follow? 01:57.430 --> 01:58.900 This is quite simple. 01:58.900 --> 02:05.200 You have three different things you need to give in the parenthesis, separated by semicolons. 02:05.230 --> 02:07.330 First is where you start. 02:07.330 --> 02:09.040 So here I create. 02:09.040 --> 02:13.300 You can see directly inside the int I create a variable. 02:13.300 --> 02:15.400 So I declare it and initialize it. 02:15.400 --> 02:20.980 So this will be the index we are going to use for the loop. 02:20.980 --> 02:24.040 And I initialize it here to zero okay. 02:24.040 --> 02:25.930 So that is the starting point. 02:26.050 --> 02:33.040 And then the second stuff in the for loop is the condition for the loop to continue. 02:33.040 --> 02:37.240 So here the condition is I is strictly lower than ten. 02:37.240 --> 02:44.230 So basically as long as I is strictly lower than ten we are going to execute this block of code. 02:44.230 --> 02:51.880 And the third parameter here is what we do with the variable with the index every time. 02:51.880 --> 02:55.540 And here I do I plus plus I plus plus. 02:55.540 --> 03:02.170 So I plus plus is the same as if you do I is equal to I plus one. 03:02.680 --> 03:05.920 This will simply add one to the variable. 03:06.490 --> 03:08.560 And this is specific to c and C plus plus. 03:08.560 --> 03:10.030 And it's quite convenient. 03:10.030 --> 03:13.030 So what we do we start at zero. 03:13.030 --> 03:15.970 We check if zero is strictly lower than ten. 03:15.970 --> 03:20.140 Yes we enter the four block and then we come back to this. 03:20.290 --> 03:23.590 So what we do is we do I plus plus. 03:23.590 --> 03:25.840 So now I is equal to one. 03:25.840 --> 03:27.820 Is one strictly lower than ten. 03:27.820 --> 03:28.300 Yes. 03:28.300 --> 03:33.910 So we enter this block etc. etc. until we reach value ten. 03:33.910 --> 03:38.680 So when I is equal to ten this condition will not be true okay. 03:38.680 --> 03:42.130 Because ten is not strictly lower than ten. 03:42.130 --> 03:47.230 And then we don't enter the block and we resume the program here on line seven. 03:47.230 --> 03:53.110 And as you can see here, a particularity is that we start to count at zero. 03:53.110 --> 03:53.440 Okay. 03:53.440 --> 03:55.360 In programming, take this habit. 03:55.360 --> 04:01.990 You don't start to count at one like you would do in real life, but you start to count at zero. 04:01.990 --> 04:06.460 So to count from 1 to 10, you will actually count from 0 to 9. 04:06.460 --> 04:06.940 Great. 04:06.940 --> 04:11.980 And we are going to come back to this for loop quite a few times in this course because this is very, 04:11.980 --> 04:12.910 very useful. 04:12.910 --> 04:16.630 And now another loop you can use is while. 04:16.930 --> 04:23.680 So I'm going to do the exact same thing we did here, which is to print that ten times but using a different 04:23.680 --> 04:25.030 way with the while loop. 04:25.510 --> 04:30.310 So first I'm going to create an int I. 04:30.940 --> 04:32.980 So I'm creating an index okay. 04:33.310 --> 04:36.400 And then the while basically while condition. 04:36.400 --> 04:43.330 So while I is lower strictly than ten I'm going to open curly brackets. 04:43.630 --> 04:46.450 And I'm going to do this. 04:46.840 --> 04:49.510 So while I is strictly lower than ten I print. 04:49.510 --> 04:50.260 Hello. 04:50.260 --> 04:55.390 So here let's say hello four and hello while so we can make the difference. 04:55.750 --> 04:59.650 And what I need to do is I plus plus okay. 04:59.650 --> 05:02.710 And don't forget the semicolon after each statement. 05:04.120 --> 05:06.700 Let's run that code here. 05:06.700 --> 05:10.390 So I'm going to clear the output and upload. 05:13.520 --> 05:17.750 Okay, you can see hello for ten times and hello while ten times. 05:18.080 --> 05:23.270 So you can see the while is a little bit different because we just test one condition and then we go 05:23.270 --> 05:24.170 inside the block. 05:24.170 --> 05:31.760 So if you want to use a counter like we used in the for, you would need to create a counter here before 05:31.760 --> 05:32.360 the while. 05:32.360 --> 05:37.850 And then you of course need to increase the counter inside the while because if you don't increase it 05:37.850 --> 05:40.820 well, I will always be lower than ten. 05:40.820 --> 05:41.060 Okay. 05:41.060 --> 05:42.110 If you don't increase I. 05:42.140 --> 05:44.900 So this condition will just run indefinitely. 05:44.900 --> 05:49.160 And this is what we call an infinite loop. 05:49.430 --> 05:54.560 So an infinite loop is when you are stuck in one loop and you can't get outside of the loop. 05:54.560 --> 06:01.430 So here, because we always increase by one, at some point I will be equal to ten and this condition 06:01.430 --> 06:02.210 will be false. 06:02.210 --> 06:05.060 So we continue. 06:05.060 --> 06:08.270 So we resume the program at line 30 okay. 06:08.270 --> 06:10.160 And here in the while we use a counter. 06:10.160 --> 06:12.230 But you can actually use something different. 06:12.230 --> 06:16.730 For example while while the push button is pressed do this. 06:16.730 --> 06:21.380 And then once the push button is not pressed anymore we just leave the while. 06:21.410 --> 06:21.920 Great. 06:21.920 --> 06:25.490 So now when to use a for loop versus a while loop. 06:25.490 --> 06:31.310 Basically, if you know how many times you need to go through the loop, use a for loop. 06:31.370 --> 06:38.930 For example, if you need 100 samples from a sensor, then go with a for loop and use a while loop when 06:38.930 --> 06:42.080 you don't necessarily know when you have to stop. 06:42.560 --> 06:49.700 For example, if you need to read data from the same sensor but stop whenever the value reaches a certain 06:49.700 --> 06:50.660 threshold. 06:50.660 --> 06:57.890 So for the example of this lesson, we can clearly see that a for loop was the most appropriate, since 06:57.890 --> 07:01.610 we knew exactly how many times we had to repeat the action.