Ethereum Foundation DevCon 6 - Layer 2s Track, 3 Nov 2022

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From YouTube: StarkNet 101 Workshop - Getting started with unlimited scalability | Devcon Bogotá

Description

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https://archive.devcon.org/archive/watch/6/starknet-101-workshop-getting-started-with-unlimited-scalability/

A 2-hour workshop introducing the StarkNet Layer 2 network, how it works, and why it provides scalability to the Ethereum ecosystem. For this, participants will learn how to harness the power of the Cairo programming language and write their first semi-complex smart contract.

Speaker(s): Omar Espejel, Henri
Track: Layer 2s
Keywords: StarkNet,L2,ZKPs

Follow us: https://twitter.com/efdevcon, https://twitter.com/ethereum
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Devcon is the Ethereum conference for developers, researchers, thinkers, and makers.
Devcon 6 was held in Bogotá, Colombia on Oct 11 - 14, 2022.
Devcon is organized and presented by the Ethereum Foundation, with the support of our sponsors. To find out more, please visit https://ethereum.foundation/

A

A

We're going to be talking in English and if you don't understand anything on the slides, please let me know no problem, but just focus on me.

A

So on the layer one we had amazing applications. We got a lot of applications very interesting, for example amms that could let you transact with different tokens, but these were very, very, very expensive right. We also had oracles that allow us to introduce data of chain into one chain right, but it was also very expensive.

A

Moving data on chain is expensive. We also had gaming, where you can have nfts very cute nfts. You can have your sword for your game, you're gone and so on. You can maybe move it to another game, but still the game was was lit, was directed by a single entity that had the control over the game, so the game Logistics, the game logic was not on chain. It was not Auto regulate it.

A

Yes, because it's very expensive right also, we had both in apps but also again, writing in the storage right into the blockchain is very expensive, so voting was also real expensive on layer one. So this is very interesting applications that we have in the layer one both that introduces problems when we are talking out costs. So we know the states. The current state of things is either we have a huge machine that is processing everything. We know this and, for example, Banks Acorn, apis companies, startups and so on, very huge machines.

A

They can process a lot of transactions very quickly and now we're looking at the blue Parts, where we are trying to create a centralized system, which is when a lot of persons can verify the Integrity of the system right. This is what we're trying to do. The problem is that this is very slow and this is very expensive and the computation repeated itself various times at different points, so it's not optimal for scalability.

A

Of course, this was a choice when we decided to create theorem. We wanted this centralization. We wanted security, it was a choice to sacrifice at that moment's scalability, but now we know better and we can do better stuff. So the question is: can we head? Can we get the centralization security and also scaling? Yes, we can do with your knowledge roles, and we are here today to talk about star Nets, so we're talking about a platformer layer 2 that is secure by ethereum. It allows you to create smart contracts, General smart contracts, it's too incomplete.

A

The cost of execution is much lower and.

A

You can create amazing things that are not possible even imaginable in the layer one, so we can get much more for each piece of gas.

A

So this is a quote from Albion session, our founder at Bangles, in the 29th of July, he's talking about the objective of starnet, which is creating a solution for scaling. That is, focus focus only on scaling theorem, and this is called Cairo.

A

So our Star Wars are experts on both the attribution machine and also creating stock systems, and there was a conscious choice not to use the evm to scale. We created a new virtual machine called Cairo. This is this WhatsApp comes choice because we believe this is a way to achieve the biggest scale.

A

And this scaling is going to it's going to come from Smart contrast with them in Cairo in Cairo is a virtual machine, but also language we have.

A

So what is Cairo currents are doing complete language programming language that allows you to create brewable programs. In this case in Spanish you can execute your Cairo program and then you can prove a smart contract on the layer 1 on assume that this a transaction was correct.

A

This allows us to have much more much cheaper transactions cost and because Pro, when the smart contract on the layer, one Valley days, that this proof is correct, it's much cheaper than running the transaction itself. So this allows us to create more to get much more scalable Solutions uh using the layer 2 in this case with cat with Chiron, starts.

A

So this is our solution. Let's generally follow-ups specifically talking about Chiron starnet, you can get extremely extremely cheap computation thanks to Cairo and we can create- and this is key- we can create interesting applications that are only be that could only be made using the layer. Two, it's impossible, practically impossible to do on layer one.

A

This is an interesting data that we got during the last week. A standard plus start startix blocks stagnant, so Star Wars. The company has different solutions. One of them is star trekx and the other one is started that we're talking about right now and both together had more transactions since July than Bitcoin lining and all layer 2's. This is something that is not very well known, whereas you can see coming from July. The blue line is the starcakes plus Stark Nets down is Bitcoin in Orange and under that are other layer.

A

2 Solutions, so, as you can see, Stark is an external, it's currently being very, very used and we have been live in Maine since June, yes, June 2020., so we are not new at this. We know how to do it. The Star Solutions is very good and, as you can see, it's very very it's been very used, and very interestingly also, is that 70 percent of that come from nfts.

A

It's very interesting, for example, with immutable with sorare interesting.

A

So now, thank you very much for coming now. We know that Stan has a lot of potential. You can create needs whenever you want. You can deploy it currently and actually, today, we'll be creating a boating application that we're gonna be trying on starnet. You can use it. Cairo is a different language. We know it, but it's also a language that everybody can use. It's not hard at all.

A

So my name is Marshall Hill I'm, a developer, Advocate server, and thank you very much for coming today. The golf today is for you to get the resources to start to start studying Cairo if you want to go into starnet and also make a small example of a boring application.

A

So now we talk a little bit about what is being done in layer, one that is very costly and we can improve what now, let's talk about? What can we do with all this power that chip computation can provide us? For example, we have a solution called ckex, it's a company that is offering high frequency trading. This, of course, is impossible in layer, one imagine having micro positions and trading with them. I don't know it would be impossible because of the course in the year. One makes no sense.

A

We talked before about voting. Voting is very expensive too, so there are also solutions, for example, snapshot X that allow us to bolt much more cheaply. Yes, so there are a lot of applications that have been already developed since I started using all this power. Another one, for example, is the government of Buenos Aires, create an application that allows you to have an identity on the blockchain as a user as a citizen, they show they chose starnet because it's very secure it's highly highly secure, and also it's very scalable and very quick.

A

So these are only some examples, but the custom is growing by the day. For example, we have tools- amazing tooling, for example, coming from hard hat, open, sepulime and chain link soon Alchemy. Those are well-known companies, but we also and maybe more interesting. We have different applications on the top, as you can see that are being created originally on the layer too.

A

So this is very interesting because it's at least my opinion is not for the company overall, but it is interesting when a company comes from Lane one and then puts its applications layer to it's great. They are using the the lower fees and that kind of stuff. However, I believe that the real power is being used, but those that are created natively on Cairo in the layer two.

A

Yes, it's a little bit like, for example, when you have Windows in your computer, Windows 98, for example- and you had this nice and cute games and then comes for example, Windows XP right, it's more powerful, you can do much more stuff and these games can be can be passed into XP okay, so these old games can be passed into the new software and they run well, it's okay. They maybe could leverage some of the power of the new operating system, but the real power comes from that that is being built on top of XP.

A

That could not be done in the previous operating system. Right, that's what we're talking about here, something that is completely different and out of the leak of the layer one we can create something very, very interesting that is impossible to create. For example, we were talking about the games that they didn't. Have the logic on chain is now possible, so imagine that you can do operations summations, multiplications divisions, whatever you can do that, because the gas is much much cheaper. So a company I, don't remember, I, know the num.

A

What is the name of the project that was creating this on chain reality topology, so topology created a game on chain and it's Auto regulated. Okay, so do you need a central limited to the sides? If you're allowed to play it or not, so it will stay forever as long as ethereum exists. This is something that is again impossible layer one and for me those the powers is going to come from that part.

A

So now the question is: um what can you create? That is completely different from what has been created in the layer, one using all these new power, all these new potential that you can find in the layer 2. that is so completely different, never done before. Imagine you can do, for example, machine learning on chain. You can print models on chain. You can create any kind of mathematical operations on chain, it's completely different and what we need is people I start building these applications that are eye-opening.

A

So uh for the beginning, you would need to start installing Cairo starnet, hey, of course, I. Don't expect to expect you to do it right now, but you can follow these QR codes for some instructions on how to install Cairo and starnet. So you can get going.

A

It's not difficult at all and say. While you scroll it, we also have a report that is called started edu where you can find a lot of educational material. I will show you the link with in a couple moments and Inside Story du. You can find a lot of tutorials on different stuff. For example, you can know how to how the cowboy syntax look we're going to look at it. In a moment.

A

You can, for example, create a token an erc20. You can create your nft, your c721 tutorials, for even more interesting how you can create your own Bridge from layer, 1 and layer, 2. Bridge, and for example, how can you create your own wallets? So you can. If you can scan this QR code, you will find all that material inside and you can get uh going by yourself without without any problem. Those tutorials are amazing and they have onboarded a lot of people into the ecosystem.

A

Also, we have a newsletter that is very nice and you will have a lot of educational material there too, and also some interesting projects happening on the on the on the ecosystem. It's also there you can subscribe. It's a soft stack newsletter.

A

And finally, what we're going to be doing today is a voting application. They will allow a person to either vote for one or zero one for yes, for example, zero for no and deploy it on the test. Nets. If you have any question until now, you can tell me this is the report that we're gonna be using. So if you want to have the report you want to clone it, you want to copy the code or just look at it feel free to scan these QR codes.

A

Any questions comments well, we'll start with the coding parts.

A

B

And I have a question actually how many of you know how to code in solidity? Can you raise your hand how many of you have ever coded in Cairo? Oh a few of you cool.

A

Coming from so late into, Cairo is very simple, yeah really really simple, and it's great that you're already working with solid.

A

Perfect you want to go to Tesla and see away and interact with with this contract feel free also to scan these QR codes. The test Nets already working with this, both team contracts.

A

A

Here, if you want to come also and I, don't know guys, do you want to add something else before we start going? Oh perfect,.

A

Okay, do you need another QR codes? uh Do you have already the the one with the contract will win we're going to use? Is this one remember please?

A

So, let's go to the counts.

A

So this is our boating contract.

A

Again, the goal is to create a contract that allows certain predefined addresses, for example, me as the admin of the of the of the boat I can tell okay. This address can vote this or address. Can both. These are the Rescue Bots, because we don't want everybody to be able to post only certain participants of of a project, I don't know, and they will be able to vote Yes or no just with one no with zero and yes, that will be all so. For this, let's review the structure and how Carol looks here.

A

We are importing our packages very similar to how it looks in python. As you can see it, then we Define its drugs, as you would, for example, in Rust flush. The grain are both counting structs, where you will be able to store the boats with yes or no. So, for example, we'll have 10 volts with yes, zero bolts with null something like that, the counting of the boat.

A

Secondly, we have border info where we store information about the Border in this case, I only very simply allowed I simply added an allowed member that it will have a one if it's allowed to vote or zero. If not, if, if this person has already vote, it will have a zero now coming to the storage.

A

This is storage variables. uh Allow you to know if you're not solid already, these are very similar to you. They allow you to map from when um from one expression to the other, in this case, for example, the first one. Now, let's go to the third one here, I am able to map and address to to a is register Bible. That, in this case, is a field, so Cairo is type it's a type language. Now you might ask yourself what is a felt.

A

Everything is a fell inside Cairo conversion to Felts and basically for our purpose right now. If you want, we can get a little bit deeper in a moment both for now in order to to get to make the most of the time, I felt it's like a big interview, a huge interior number. Okay.

A

So, in this case, as you can see, the address has not address type as in solidity. It's a field. Okay, so we're mapping an address. There is a failed to a field called, is register that will have a one or zero or whatever we haven't defined it yet and on the other ones. We are mapping our information and, interestingly, in the first one we are mapping nothing, yes, nothing to a structure about Counting.

A

So this allows us to read or write into the memory. That's as simple as that I can read this or I can write into the memory using these ones, so using the storage variable boat in status and if we read it and if I I will go right now to the deploy contracts.

A

So this is the deploy contract I'm using right now, boilinger, which is a Blog Explorer for starnet.

A

If I go to the read part of the contract, I can see what both in his status is doing using a getter function that we will see in a moment. You can see the status of developing right now, because nobody has both Jets. We have zero codes with this three boats would know so that is the storage we are reading right now. This storage variable will I get our function that we'll get to that in a moment, and also we have the boring info and it's the same.

A

Everyone goes into this, but basically we're storing information into the uh in this into the storage of the of the blockchain. Now, let's go to the Constructor looks very similar. You know we're doing an initialize, your your contract, with your deploy it you have to Define certain inputs as insulated, exactly the same name, so this Constructor will ask for three different input. Bibles, as you can see now we can. We can view how the a function looks into Cairo, it's very simple, very similar, also to to Python, and what is important here is this part?

A

These are the inputs, the explicit inputs to this function, in this case the inputs for the Constructor that we have to provide it when we deploy this contracts.

A

So I'm asking for an admin address the person that's going to be able to to manage this contracts with a felt again, then the number of addresses that will be able to vote and, finally, the disappointed.

A

So it's important to know that Cairo is a low-level language, so here we can manage the memory we have to manage it, so the register addresses is basically a vector with a different addresses. Arrival to both I can add five six, seven, eight whatever, and this pointer felt points to the start of that Vector. But you would even notice that this, the logic behind it is that this is pointing to the start of this array of different addresses.

A

But you won't, you will notice this do, as you will see, then we're basically using a contract because we have open simply on top also of stone it. So you are able to use a very secure contracts thanks to open sampling and we're using the owner will contract from our principaline before I import them here.

A

So I imported The, Honorable, a contract and the possible contract libraries from openstepperling owner will basically defines who the owner is of something and possible. It allows you to post a contract in case of an emergency say that, for example, my application is being hacked, so I can pause it as simple as that, but also we have erc721 Logics and erc's 20, so you can use it with open supplement. That's very, very useful, very, very useful, any question. Until now we have seen the Constructor we can see in the storage variables Strokes how to import.

A

How are you finding Cairo too difficult? Or is it nice any questions? Yes,.

A

A

Sorry, what was the question.

A

Yes, for example, we have, in this case we will be using addresses that are in an Excel in hexadecimal format. Right, it will simply be converted to a field behind it will be.

A

We will actually deploy right now, our control using hex, hexadecimal values, and you will have to convert two Fields, but you also could compare it to a field and also you play with this no problem right now. We can think of it like big integers, and we can get deeper into that any other question right now we have seen Constructors towards variables, Strokes.

A

Well, perfect, okay, so here our Constructor- and with this we can deploy our contracts.

A

Also, this, um as you can see, the structure of the contract is very similar to solidity. We're trying to follow the guidelines of smart conducting solidity. You have Getters, you have the Constructor and the format is very similar. Also, if you go to this contract is very well commented, so you can know what is happening.

C

C

A

I think you guys can yeah.

B

Sure so, there's no inheritance in Cairo. You don't inherit your contract. What you do is you import your function, so if you're looking at the the top of the uh of the contract up there here.

D

Is importing a templates developed by open the printer is importing the full contract.

B

Which is called audible, so it means that he Imports all the functions that are inside of this contract and inside of this contract. You know it creates. It creates a few variables that can be initialized, and um one of them is called the initializer which is supposed to be called during this Constructor does.

C

That make sense yes, I was just curious because, usually that's thread.

D

So it's not explicitly it's not automatically initialized, because um because it's not like the contract is not ownable, it Imports some function and it has no way to know that this is the specific context of the Constructor. So you need to initialize it explicitly regarding the question on felt earlier: um I'm, not sure what confuses you, but when you're looking at variables in solidity, you know at the bottom of it at the end of the day, it's a number and Cairo is a fairly new language.

D

It will get better in the next few months, but right now it treats everything as a number. So if you want to perform actions when you need strings, you basically need to assume that you receive them as numbers. You convert them, you do your operations and you do all this kind of stuff make sense, sort.

B

D

Yeah, so a felt is, as you mentioned earlier, I think I heard you say it it's a field element. So Cairo is like the felt you can't think of it as a big end, but it's basically a number over a big film The Field. That is a prime that does indeed uh um field integer, mathematics and arithmetics. That makes sense. So it's really like you can treat it as modulo operations. The only time where it gets weird is for divisions, division, sucks, I, don't like them.

A

No problem with that, so, for example, we were talking about the honorable contract. This is the one that were important, so we have it here locally and we're importing. For me, this is the owner which comes in a namespace, so we're importing these functions.

A

Yes, there are no inheritance in Cairo perfect, so going back to I can't read two.

A

So we import these functions honorable and possible from functions inside the ownable namespace and inside the possible namespace. You can yeah and there's a question.

E

A

D

Open Zeppelin is working to create the standard implementation, so any kind of contract you have on solidity, you're used to have that is done by open, Zeppelin we're walking towards having that. That being said, I mean it takes time to develop contracts that are secure and everything. So if you want to develop them, you should it's worth it. It's fun, and you know you may develop stuff that gets used by other people, which is great.

A

This actually principally the contracts incredible principling, they have a lot of contributions from people outside the community, so that will be where it also.

D

If somebody manages to write a Cairo contract that is the equivalent to this taking contract in synthetics, which is used by everyone, I'll buy you a beer.

A

More than a view.

A

It will eventually happen. It's very if you it's one of you, okay, so we got our Constructor and then we can get to the here. We're using the initializer function inside the ownable namespace, and then we go to the Getters is very simple functions by definition in Cairo are private not like solidity. So here, if we want to have Getters functions to read information, we have to explicitly tell that they are getters so and something that I forgot to mention before. But this is the way like very similar to how you do it in Python.

A

How do you define that this has a particular set of properties? This function that that is coming in this case with view we are defining, get our functions functions. What you can read from so right now we're creating this admin function. That, as you can see, is exactly the same format as it comes in open sapling, for example, in erc20 or erc721 simply reading who the owner of the contract is so, for example, if I go again back to the contract, deploy control here, I can read who the admin is.

A

As you can see, this is a field, but if I convert it to hex, this is the owner of the contract. That is myself.

A

Is this same direction so talking about wallets, it's a good opportunity right now. You can use right now, RDM X, which is this one and also Bravos. That is this other one very recommended you can use the Standard faucets you can simply put in Google started faucet and you will be able to send yourself some fake it, so you can start making some interesting things using girly or more.

A

Interestingly, you can also Bridge your own it from the girl testnet in in the layer one into the layer to start it, for example, here we're using program I can I can ask for some fake it send it to my metamask, for example, and then using the bridge I can connect my meta mask, which is currently my my wallet in layer one and connect, for example, RDX here as my wallet layer, 2 and I can reach these fake it from girly layer 1 to layer 2.. So this is also very interesting.

A

It's the same thing as asking for it in the faucets, so going back to the contracts.

A

We have another gear function here. It's also a very typical open setting style function where you, what we are posting we're asking when we think if this contract is currently post, very simple and then more interestingly, here we have a view function to know the boring status is the one that I showed you before it will.

A

Let us know how many people voted this, how many people bought it now as simple as that again, you can see in this function that we have an explicit argument and by now you are already asking yourself what is this?

A

What is this inside these keys? These are implicit arguments. This is something that is different from other languages. You might not seen that before, but basically, uh these repeat themselves all the time: Cisco pointer person, pointer and Rich check Pointer, while interacting with the memory here. So we are talking that these are Pointers actually into a felt and to a stroke. Circle has built it no problem. No, we will need to get that. That is something that we're repeating in each function.

A

It doesn't matter. The real use is here, so we ask in here for an explicit argument that is about Counting. Sorry, sorry, we're asking for nothing here: it's empty the inputs and the output. Is this a status, a variable called status? That is about counting structure that we saw before again. Kairus type is a type language. This helps for security.

A

Any question until now for this function, for example, yes,.

A

Yes, this is again, you can read it. You can read from the gates boring status. This is the one that I was showing before and currently the votes are yes or no. This is practically in the structure we have and Define here this one. Both. Yes, both know it's exactly the same here, Okay, so foreign.

A

Explicitly telling these functions that you have passed them so they, for example, when we are reading from the from the storage you have to provide these functions, that the sorry, the pencil pointer and the Cisco pointer. You have to provide them and they go into the read function so inside here our implicit function, implicit arguments, you don't see it because they are implicit but.

A

Yes, exactly this input functions. If I take them off, they will have an error, no problem, it's it's not hard to to to get used to them, and also you can see each function that I adding here has them repeated. So no problem with that.

A

Okay, also, we have an overview function where we are getting the status of a motor and.

A

Just if you were simply reading into the voter info, a storage variable that we have before using the argument reads so now going deeper into this. We can read and write from this storage function. In this case we are reading and, as you remember, this search function asks us. Why do you surround device and it was precisely a failed? So if we provided a field then it will return us, let's see once does it return.

A

Yes, if we provide an RIS, it will return us about our info structure. Okay, so here I'm reading from it and then we're returning it simply as that status equal status, because the name of the variable here is a status.

A

And to see an example of how to write exactly the same, the same storage variable that we saw before motor info. We were able to read from it if we are imputing with the address- and we know we now know that it returns an instructs okay. So now we can write using the argument right. We can write on it, so we're writing on the storage of our contract and right now. This is basically an address. We will go deeper in the moon over it, but this is an address for this address.

A

Please map this instruct okay, very similar to how you look at it in solid. Yes,.

A

Sender is a I think we have it here, get code address with this you're, getting the address of the of the contract that is calling this this contract. So, for example, in this case, this is the most important function is the both function. So what it does is simply it's getting. The address of the color is turn it and then we'll reviewing the information of this person to see if this person has already bought or not, because we can only allow them if they have bought it and just in a moment we'll go into that.

C

C

A

You repeat the question a little bit louder. Please.

C

D

Like an address, there's no notion of msg.value in stock net, because there's no native currency everything's in near C20, so there's no value attached to a call. There's no um and.

B

D

No payable function that answer your question.

A

Okay, so yes, um so, let's go quickly into the most important function. The two most important functions, the register voters- and this will help me to and talk a little bit more about recursion that we use in Cairo.

A

So again, as you can see, we have the implicit arguments as always, and then we are asking for two explicit arguments. The register address Lane this. This is the the length of an array, and the second value is the array itself. So first argument is the length of the length of this array. The second argument is the the array by itself, then what we're doing here is and again you can see all these contracts in the report.

A

I showed you before isn't started with you in case you are, you want to follow it closer in your houses and then what we're doing here is simply- and this is a at least a classic function of Cairo that is using recursion. So right now we don't have Force in Cairo, you have to use precaution, and this is a classic function for it.

A

When we review here is that uh it is the end of the recursion. So if we have already passed to every each of these different members of the array that is, if the length is zero, then we can return and the recursion is finished.

A

Then he will create a small, a small struct, the water info. Do you remember we defined the stroke called motor info here we are creating this butante info, where we have this new motor info so empty anything here that allow is equal one. It could be zero, for example, so this function. What it's doing is that each of the address that I'm providing it will register them as voters, and we tell we tell us that they are allowed to vote okay and then continue a little bit with the recursion.

A

What we're doing here is writing into storage into the storage variable register, motor.

A

Yes, this one we're mapping, as you remember before we mapping an address to a number, so this is an address. What we have here is this is the array as very similar, as you would do it in Python, for example, on all languages. You have that right and you can index to it using the square brackets. Okay, so I am indexing in the inside.

A

This array, for this could be a number like one or two or five depends on the number of address that we are adding, and then we say that the value for that address is one. We are simply mapping it here, and then we become the recursion part.

A

Here we are reading again the same function and providing the length, but this is a lower length, as you can see, if we have, for example, five different voters that now we are providing it with four okay and we are sending it with the register address and then it will repeat, it will repeat until it passes through each of the different addresses and it is starting for from the last one up to the first ones.

A

I know what this looks a little bit crazy here using caution. Bots, it's no problem, you you can get used to it and I think that this will improve in the near future. Right.

A

Yes, well, that's a good question.

A

The question is that what happens if you get into an infinite recursion.

D

um You, okay, so there's there is the there's an answer for today and an answer for tomorrow, but basically there's a form of gas metering in starknot, just like in ethereum, and if we reach a match maximum number of steps, the sequencer will recheck your transaction today, you're, not you don't pay for this kind of transactions. They're just rejected tomorrow, um you will be. It will be like a fake, transactional ethereum. You will pay fees for the execution that led nowhere.

A

Good perfect any other questions for a moment. Okay, so simply we have a recursion function here again, it's not that hard and it will improve we're talking that Cairo is a low level language and we have to be very honest and conscious about that.

A

And finally, let's go to the last function: that is the Boating function. This will allow us to call a function as, as you can see here, it's an external function. External function simply means that we can write on the storage using it. Okay, not only reads, but we can hear right into the storage again. We have our implicit arguments.

A

We have an explicit argument called both and here don't mind this part simply telling the memory that we will be using the compiler that will be using local variables. We don't need to go through that. We're called the possible function from from open sampling contracts. Specifically, the function called assert, not pause. It checks that if, if this control is false or not, if it pause, this person cannot vote as simple as that, then you get the caller address. This was a question from before.

A

With this function, we can get the address of this color, we're storing it inside the color function. Then we can read the information of this color of this address. Using the reads. Argument from this touch variable, that's already the nympho, and then we are simply reviewing. Is this person can vote or not? If they have a low zero, then they cannot vote.

A

Then we're creating a new bullet border info extract that it says that this person has already bought, because we wanted to vote again.

A

We are writing on the storage here. Everything here. We already know that and finally, we are updating the status of the boats with the vote of this person. If this person voted yes or zero in this case, then it will update that with zero, the count with zero and if they bought it. Yes, in this case, one for example, then it will be updated. The count will be updated with a sum that we have here.

A

And finally, we are updating the final status of our update, the story of our voting and storing it into the storage. As you can see, this function is scheme and if we go to the deploy contract, we go to the right contract and then I can vote in this case. This is the function I, don't remember where I say and that I think so. I will go to my Bravos wide in here. I was in my origin before and let's see, if it allows me to vote so I will vote with that.

A

One and I will be able to sign this transaction because this address is registered to both I did when I deploy it and right now what it this is the transaction hash, and we have to wait for a test to process this, and we will have our bolts now. How can you deploy these contracts? You can deploy it using the command line tools by its targets or also, and my preferred ways to use protostar protostar is a tool created in the image of Foundry.

A

It has the best practices from Foundry and also some from haircut sorry from profile. So it's very interesting. It helped us to to test, but also to deploy. So if I go right now to my command line,.

A

This is how deploying this contract looks like so basically I'm saying entering protostar, deploy this a contract that is already compiled by this moment, and what I want you to notice here is the part of the inputs it took before about the Constructor, a setting for three different inputs. First, one is the owner. The admin of this voting, second, is the number of persons of register addresses that can vote and, finally, the actual addresses. So this is how they look.

A

This one, as you can see, is a hexa, a hexa value, and this is the address that is the owner of this contract. Then only one person or one address can vote this one and we can simply deploy it run. It like like this photo store is very good. It's very usable, it has amazing testing functionalities, but you can also deploy your contracts, and that is simply the content that we deploy here and as we as we can see, we already bought it.

A

If I go to read contracts, we should get a boat in status where we had a boat with yes, we're number one, it updated and zero is still no I could note both again because uh directly theoretically, I should not be able to vote again. Let's see what happens.

A

Oh, it should be it should it shouldn't pass right now, but let's wait for it, so that would be the the main part of the workshop you. We have three minutes. Two more questions.

A

A

The implicit right now here, I, don't have any, but they can change depending on what you're building.

A

Can you think of a scenario.

D

And when do implicit arguments change every.

B

Time they're used.

D

Basically, um it's a it's a bit of a deep question. The workshop is about to finish. So, if you want let's meet outside and we'll we'll give you a a more definitive answer.

D

A

I think I have another message here: hey will I look for it any other question in the meantime, I.

D

Have a question for the audience before we wrap the the workshop up. Can we get just get a quick show of hand who learned something during the workshop cool who thought this was too difficult?

D

Who thought this was too easy?

D

Okay, fine! So it's great! This means this was spot on. Those of you still are hungry, don't estate. Ask us question: come on our Discord go on our resources! Look at what we do, as also as Omar mentioned, like most of these things, the Paradigm you're used to that you're used to how you write smart contracts, how you deal with Scholars and stuff, like that, this syntax is a bit different.

D

The tooling is a bit different, but you can and will Master Cairo it's just a matter of just like trying, and this will give this tool will give you extreme power in your blockchain applications. So if you're looking to go more to do more and go beyond what you can do with the evm I invite you like do take a look, it really is powerful and will let you build super cool stuff.

A

And again, this is the QR to the educational resources. You want to go, look at them, we'll have a boots on Thursday and Friday. You can ask, ask any question come with us and finally, regarding the question, the the error messages. This is how they look.

A

So if this assertion true or false fails, then it will print this mistake motor info well, thank you. Thank you very much.

A

Well, it depends on the on the wallet, uh let's see, for example, this case a certain Lounge.

D

Yeah, so what your question is, what does a narrower message? Look like from the browser perspective. Essentially, you'll get a failed transaction like you do on ethereum and the trace like the way it shows up is kind of ugly. To be honest, it's still very rough around the edges. There's a lot of info. That is not necessarily relevant to you, but the message, the error message will appear somewhere and you'll, be you know able to know where the error is from in general, this thing works, and this feels scale.

D

This thing scales ethereum right now, it's a bit rough around the edges, meaning that it's not all pretty there's a lot of info or not enough, but uh but it works and that's cool. That's cool.

A

Though this is how the error looks like, as you can see, that's the message that we saw before in there yeah explore info your address is not allowed to boot. Then we will have a boot. Please feel free to ask any questions, and thank you very much for coming.