Hey all, does anyone know if there are any existing repos with templates for a bid / ask systems for erc721s?

Crypto punks had this mechansim built in but not melt in the ERC721 standard. We have this in house but have not made it publicly available yet.

thanks, I'll take a look at their repo. What's the trick to automatically match outstanding bids to asks?

The trick is maintaining a separate struct.

and keeping only one bid and one ask

lol

quite a simplified approach. It's ok since the liquidity for a NFT is not that high anyways.

but on a marketplace like rarible / opensea, you have multiple bids / asks at different prices to account for

Hope contract companies like OZ can develop an extension for this.

not sure if they do it on chain or not, if yes, that's quite expensive, if no, that is nothing impressive.

I suppose if they are onchain, you can keep an array / mapping of bids and asks, and on sending one check the other list to see if you're beating out the minimum, price, and if so match those two orders

I'm not an expert on this, but I would assume maintaining an ordered data structure to resemble an orderbook on-chain is quite expensive.

yes, it would be expensive to call and manipulate

Curious about how rarible and opensea did it.