[spopejoy]

It's possible, but impractical:

- Pact executes in a runtime environment that at a minimum ensures any ED25519 signatures on the transaction are valid, such that code can then test the validated public keys to enforce authorization rules. So this would need to happen before each transaction, which would assuredly be super-expensive gas-wise.

- Pact modules (i.e., contracts in the Solidity sense) export functions on-chain that can then be imported/invoked by other modules by name, thus allowing safe inter-contract communication, on-chain services, and other nice things. This model is very foreign to Solidity where inter-contract communication is poorly supported; best practices there dictate copy-pasting approved code (c.f. ERC 20 tokens) and hosting all functionality in-contract.

- Pact being interpreted is hugely valuable on-chain, as you can directly inspect human-readable code, as opposed to EVM assembly/opcodes. This is more of a philosophical point though.

- Other things, like supporting direct storage of JSON objects in the database, exporting Pact types as JSON (which you get for free in the Pact runtime), key/value db functionality, transaction history at the db level, support for governance in upgrades -- all of these would need to be coded in as Solidity code, with great computational expense.

The biggest issue facing Solidity developers today is the sheer cost of best practices: ensuring you handle overflows right (ie don't use math primitives but call an approved function), planning for upgrades/data export, you name it: you have to use that code and pay that gas. The environment really needs to provide a lot more "free" functionality than it does today to change this reality.

[flashmob]

> best practices there dictate copy-pasting approved code

Not entirely true. In Solidity, you don't need the whole code to call other contracts, you just need their interface (function signature) and you can call any contract.

You'll see all the best practices use interfaces these days.

Agree with all other points, especially about the math safety - there needs to be more support for financial math too.

[spopejoy]

Hmm ... would love to see an example of Solidity contracts calling pre-existing Solidity contracts as a best practice, especially given the difficulty of verifying the state of code on the blockchain.

In Pact, when you load a module, all references are aggressively resolved and directly linked to the calling code. In Ethereum, if the contract you're calling doesn't have the interface you thought it did, you won't find out until you actually call the code.

My understanding was you really can only trust your own code in Eth, that you can't rely on a pre-uploaded contract (like a safe math contract) -- and you certainly can't extend one safely.

[woah]

So I can't send a contract in your language some signatures as byte arrays and have it validate them in its logic? Any program that signs things also needs to be able to produce block chain transactions? Just an initial question, I'll read more on your site.

[spopejoy]

We haven't seen the use-case yet where the (signature,payload) tuple is not isomorphic to a transaction. Yes, in the case of multiple, distinct payloads, you'd have to break those into separate transactions, but that seems like a very specific use-case that doesn't sound very "transactional".

Pact's philosophy sees a blockchain as a special-purpose database, for distributed transactions, so it's not designed for many "normal" database cases, namely bulk operations, searches, heuristics, etc. The use case of accepting multiple signed payloads sounds suspiciously "batchy" to me. Also, Pact is "success-oriented": we see failures like a bad signature as something that should fail your tx only. This is a way of avoiding dicey control-flow logic.

So, if a single payload is what you need the signatures on, you simply design your contract API/function call to have the specific function to handle that data (store it in the database, whatever), and let the environment check the signature.

EDIT: Pact is actually `([Signature],payload)` -- ie, you can sign the same payload multiple times

[woah]

Signing the same payload multiple times would work for my use case (channels). I also need to accept transactions signed by at least one of two keys. I suspect this might be possible too. However, I can imagine that anything more complicated would go outside of the system you have designed. I haven't had the chance to learn your language, but I would be wary about it either being too limited for edge cases that most real world stuff is going to have, or turning into a "universal framework" antipattern.

[spopejoy]

> I also need to accept transactions signed by at least one of two keys.

Keysets are designed for precisely this; what's more this rule can now be persisted.

> anything more complicated would go outside of the system you have designed.

Always a possibility of any PL, especially running in a blockchain. Pact makes less assumptions about use cases than most however. It's imperative, allows functions and modules, and offers a database metaphor. That handles a fair number of things.