Loop block allows us to repeat behaviours . Created by Brit Cruise.
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- what is the symbol at the left, the small orange box(1 vote)
- That is the NXT symbol , it is there because at the start of every program it runs that and then it runs any thing it encounters.(3 votes)
I'm just using two tones here, but you could have very large, or subsets of your program, where you get to a point, and you say, OK I need this to repeat, based on some condition. So to get into loops, the block is right here. If you're working under the complete pallet, you will find it under Flow. Here I'm going to click and drag and drop it somewhere here, doesn't matter. I'll put it here. And as you can see, the loop is actually empty. So if I run this program, I won't even get to these tones, because it will get stuck here. I'm going to drag the sound blocks inside our loop so we can do something. I will go ahead and run this program, to see if it's working. [BEEPING] What if we want to do something a little more interesting? Perhaps we want to terminate this loop based on some sensor condition. So click on the drop down box, and select Sensor. Now a bunch of settings pop up. First it wants to know, OK, what setting, what sensor, do you want to use to control the loop? And in this case I will leave it on Touch Sensor for now. And now I'm going to plug the touch sensor into port two. It could be any port, I'm using port two right now. You need to select the port that this sensor is plugged in to. And finally, the action is asking us, OK, what action will cause this loop to terminate? When I execute the program, it will jump into this loop. And every time it hits the end of the loop, it will check, is the button pressed? And if it has not been pressed, it will continue to loop. And when I press the button, it will terminate the loop. So let's run this and see how it goes. [BEEPING] OK, I'm going to press the button in three, two, one. And it worked. So this is very interesting, because if you think about it, we could have even a color sensor controlling the loop. Perhaps when the color sensor saw red, or when the sound sensor detected a clap. [CLAP] Aside from that, we can also control the loop based on time, which means we could put in the number of seconds we want it to run for. Below time, we have count, which tells us how many times a loop will iterate. Every time it hits the end and jumps back to the beginning, you can think of that as one iteration. So if I put the count to 2, this loop will just run twice. And the final method to control a loop is based on logic. If you select the Logic tab, it will be asking for a true or false. And this is a value, which you will manually wire into here. And I will leave that for another video. The last thing to remember about loops, aside from how they can be controlled, is that they can be nested, which is very powerful. For example, nesting means you can drop a loop inside of another loop. Now sound will be helpful here, because we will be able to listen to what's going on. First, I'm going to drag a sound block inside this loop here. So our program will begin, jump inside the main loop. Then it will hit this sound block, play a tone for 0.5 seconds, play the next tone for 0.5 seconds. Then it will hit this interior loop, which we currently have as running forever, which we probably don't want, because it will get stuck there. So I'm going to put the count to 2, which means when we get here, it will run this loop twice. And inside the loop I have a new sound block, which I will put to Tone, and I'll play a lower tone. So we'll be able to hear when we fall into that loop. After our two iterations of this loop, it will break out, hit our main loop, which will jump back to the beginning, and the process will repeat. So let's listen to what's going on here. I will run the program. [BEEPING] So when you hear that lower tone, that is when we fall into the interior loop. And nesting can be done many times. I can put two loops beside each other here. I could even put a third loop inside here. And so on and so forth. So with nesting and control, you can do pretty much anything you can think of, in terms of repeating behaviors.