fmg-core

Force-move Games: Core

This package contains the contracts and js libraries for the core of the force-move games framework.

The core provides the format of the states that are exchanged and the rules that govern the interpretation of these states.

Test contracts

Some contracts we use are libraries -- namely, State, Rules, and CountingState (in testing). Libraries are meant to be included in contracts, and not called externally. For reference, see some remarks by the Solidity team.

In spite of this, Solidity compiles library contracts that return structs, and produces a proper abi for external/pure functions. (It does not, however, produce a proper abi when an enum is used in a library.)

struct Foo {
    uint256 bar;
    uint256 baz;
}
// an invalid function in a library. Solidity produces the correct abi
function(Foo memory foo) public pure return s(uint, uint) {
    return (foo.bar, foo.baz);
}

contract SampleContract {
    enum Foo {Bar, Baz};
    // an invalid function in a library. Solidity produces the incorrect abi, which has
    // the type "SampleContract.Foo" as the type of the input `foo`.
    function(Foo foo) public pure returns (uint8) {
        return uint8(foo);
    }
}

However, external calls to these functions raise a runtime error. Therefore, to test a library SomeLibrary function foo, we define a test contract that imports Library.sol, and delegates foo to Library.