Vyper/community

Tools & Resources https://github.com/ethereum/vyper/wiki/Vyper-tools-and-resources

Michael Egorov

@michwill

E.g. a: uint256[3] = [convert(0, uint256) for i in range(3)]

Or even a: uint256[3] = [convert(0, uint256)] * 3

It's probably hard to do all-vyper list comprehensions, but even for just constants (e.g. no variables) it's an easier first step

Of course, "clear" function will do too

Bryant Eisenbach

@fubuloubu

well, we probably have some leeway over list literals because that goes through a Python interpretation first to see if things can be done to reduce it like constant folding. I think list literals of the second type seem like a reasonable addition. Can you propose that as a VIP?

Alexander

@alexangelj_twitter

Is there anyway to convert a timestamp into a string?

Can anything be converted into a string?

Bryant Eisenbach

@fubuloubu

no, I don't think so

bytes are compatible I think

since string is just ASCII bytes IIRC?

also, gitter migration went smoothly than I expected

Alexander

@alexangelj_twitter

I want to concat a string and a timestamp in the contract but it doens't seem like I can do that, so I'll have to put the concat string as the parameter?

Bryant Eisenbach

@fubuloubu

yeah probably. what are you trying to do?

Alexander

@alexangelj_twitter

I am creating four tokens from a factory, each token has a timestamp that is unique, I wanted to concat a symbol (string) with the timestamp, and pass that as the token symbol, but it doesn't seem like I can do that in contract, so instead of giving it a unique string symbol, I just gave it a new variable tokenId which is a bytes32, and I concat the (keccak hash of the symbol and convert timestamp into bytes 32)

I wanted each symbol of token to be "SYM1577678400" as a string, but I can just have it as bytes32 I guess

Bryant Eisenbach

@fubuloubu

oh, weird I see

ya, you can't do that yet lol

string parsing is... expensive

also, timestamps can be manipulated by miners yada, yada

Alexander

@alexangelj_twitter

yeah haha, I tried to get creative but wasn't really worth it, then I realized I should just use the address as the id...

Bryant Eisenbach

@fubuloubu

Yup!

Charles Cooper

@charles-cooper

@fubuloubu we could do some pair coding today if you want

Alexander

@alexangelj_twitter

I want to use the @nonreentrant decorator but I am confused by what <key> should be?

Alexander

@alexangelj_twitter

Also, another question: can this function be reentered?
self.mint(msg.sender, amount)
return self.asset.transferFrom(msg.sender, self, amount)

I suspect it could when transferFrom calls msg.sender

Bryant Eisenbach

@fubuloubu

Well, that makes an external call to self.asset

If you trust that contract it's unlikely to do any harm i.e. if it's a token you've created

If you're making something that let's any ERC20 token be that asset, it's worth considering the token could be compromised

But msg.sender doesn't do anything special there, just an address variable

But mint probably wouldn't cause harm by itself, it doesn't impact any internal state of the contract

Alexander

@alexangelj_twitter

self.asset is a trusted contract I create, but in this case msg.sender could be a malicious contract right?

Bryant Eisenbach

@fubuloubu

It could be, but if your token contract doesn't communicate to the initiator of your method, you have nothing to worry about

Félix Robles

@Findeton

in vyper, can a payable function send money to somewhere else?

Michael Egorov

@michwill

Is it possible to do something like import a as b? When I'm doing it, vyper complains about unknown interface and it wants import a as a

Bryant Eisenbach

@fubuloubu

@Findeton yes, you can send from inside any function, including payable ones

@michwill unsure, the import support is sorta new and may be a little fuzzy around the edges. If it's not working like how you expect, I would open an issue

Michael Egorov

@michwill

vyperlang/vyper#1753

Bryant Eisenbach

@fubuloubu

👍

Félix Robles

@Findeton

@fubuloubu how can I check the balance of the contract's address?

Bryant Eisenbach

@fubuloubu

self.balance

Félix Robles

@Findeton

thanks!

Aristotelis Triantafyllidis

@Totoual

Hi, is there a way around of concating lists of bytes32 other than manually adding each element in the concat() function? I mean I am not able to pass the list inside the concat function because it doesn't support it.

I need something similar to this.

    temp: bytes32[BATCH_SIZE]
    temp_from_supplies: bytes32[BATCH_SIZE]
    for i in ragne(BATCH_SIZE):
        id: uint256 = _ids[i]
        temp[i] = convert(id, bytes32)
        supply: uint256 = _from_supplies[i]
        temp_from_supplies[i] = supply

hash: bytes32 = keccak256(concat(temp, temp_from_supplies))

Bryant Eisenbach

@fubuloubu

I can't see exactly what you're trying to do, but currently that is the pain we have when working with hashing types. @charles-cooper is working on the ABI encoder, which will make this significantly easier to do

You will just have to do hash: bytes32 = keccak256(abi_encode(_ids, _from_supplies))

It's probably our biggest missing feature at the moment

Also will allow us to do data passing on calls like ERC721 transfer

Aristotelis Triantafyllidis

@Totoual

Hmm thanks for your response. So this is not implemented yet right ? I am creating a hash of some items along with a signature that I receive and I am verifying the address.

Bryant Eisenbach

@fubuloubu

Yeah, not yet. I mean, you can do what you're looking to do today, but it will be significantly easier once the ABI encoder is complete.

It's actually kind of cool that concat(bytes32[N], bytes32[N]) works to give you a string of bytes. I don't think I've seen someone do that yet

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