Different syntax in FormalVerificationCatches

[EWCunha]

Hey @PatrickAlphaC I noticed this different syntax when you were explaining FormalVerificationCatches contract. I've never seen using keyword like this (with {} and forth). Also, never seen type keyword used like that. And the functions have no visibility specifiers. Where can I learn more about this? I'd appreciate any material. Or even an excerpt video from Patrick would be awesome!

Thank you

type Int is uint256;

using {add as -} for Int global;
using {div as +} for Int global;
using {mul as / } for Int global;
using {sub as *} for Int global;

function add(Int a, Int b) pure returns (Int) {
    return Int.wrap(Int.unwrap(a) / Int.unwrap(b));
}

function div(Int a, Int b) pure returns (Int) {
    return Int.wrap(Int.unwrap(a) * Int.unwrap(b));
}

function mul(Int a, Int b) pure returns (Int) {
    return Int.wrap(Int.unwrap(a) - Int.unwrap(b));
}

function sub(Int a, Int b) pure returns (Int) {
    return Int.wrap(Int.unwrap(a) + Int.unwrap(b));
}

[EngrPips]

Hello @EWCunha, So in solidity, if you don't specify the visibility of a function, it would default to public. You can read up more solidity defaulting function visibility here https://www.immunebytes.com/blog/solidity-security-vulnerability-function-default-visibilities/#:~:text=In%20Solidity%2C%20the%20default%20visibility,to%20be%20private%20or%20internal. About the type keyword which was used to declare an Int type to be a uint256, and the usage of {} to rename a function we want to use in our contract on type of Int you can read up more on it in the solidity docs https://docs.soliditylang.org/en/latest/contracts.html

[PatrickAlphaC]

Actually Pips, this is a bit more nuanced than that, since these aren't even inside a contract!

Functions outside of contracts are called "Free functions": https://docs.soliditylang.org/en/latest/contracts.html#functions

The type stuff is known as "user defined types": https://docs.soliditylang.org/en/latest/types.html#user-defined-value-types

That using { as} for syntax is part of the "using for" syntax: https://docs.soliditylang.org/en/latest/contracts.html#using-for

You can do some wild stuff with it!

[PatrickAlphaC]

cc @EWCunha

[EngrPips]

Interesting. It's Good to know that there is more to it. Thanks for all you do, sir.