mirror of
https://github.com/pezkuwichain/pezkuwi-subxt.git
synced 2026-06-23 10:51:10 +00:00
Benjamin Kampmann
102 lines
3.3 KiB
Rust
102 lines
3.3 KiB
Rust
// This file is part of Substrate.
|
|
|
|
// Copyright (C) 2017-2020 Parity Technologies (UK) Ltd.
|
|
// SPDX-License-Identifier: Apache-2.0
|
|
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
//! Voting thresholds.
|
|
|
|
#[cfg(feature = "std")]
|
|
use serde::{Serialize, Deserialize};
|
|
use codec::{Encode, Decode};
|
|
use sp_runtime::traits::{Zero, IntegerSquareRoot};
|
|
use sp_std::ops::{Add, Mul, Div, Rem};
|
|
use crate::Tally;
|
|
|
|
/// A means of determining if a vote is past pass threshold.
|
|
#[derive(Clone, Copy, PartialEq, Eq, Encode, Decode, sp_runtime::RuntimeDebug)]
|
|
#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
|
|
pub enum VoteThreshold {
|
|
/// A supermajority of approvals is needed to pass this vote.
|
|
SuperMajorityApprove,
|
|
/// A supermajority of rejects is needed to fail this vote.
|
|
SuperMajorityAgainst,
|
|
/// A simple majority of approvals is needed to pass this vote.
|
|
SimpleMajority,
|
|
}
|
|
|
|
pub trait Approved<Balance> {
|
|
/// Given a `tally` of votes and a total size of `electorate`, this returns `true` if the
|
|
/// overall outcome is in favor of approval according to `self`'s threshold method.
|
|
fn approved(&self, tally: Tally<Balance>, electorate: Balance) -> bool;
|
|
}
|
|
|
|
/// Return `true` iff `n1 / d1 < n2 / d2`. `d1` and `d2` may not be zero.
|
|
fn compare_rationals<T: Zero + Mul<T, Output = T> + Div<T, Output = T> + Rem<T, Output = T> + Ord + Copy>(mut n1: T, mut d1: T, mut n2: T, mut d2: T) -> bool {
|
|
// Uses a continued fractional representation for a non-overflowing compare.
|
|
// Detailed at https://janmr.com/blog/2014/05/comparing-rational-numbers-without-overflow/.
|
|
loop {
|
|
let q1 = n1 / d1;
|
|
let q2 = n2 / d2;
|
|
if q1 < q2 {
|
|
return true;
|
|
}
|
|
if q2 < q1 {
|
|
return false;
|
|
}
|
|
let r1 = n1 % d1;
|
|
let r2 = n2 % d2;
|
|
if r2.is_zero() {
|
|
return false;
|
|
}
|
|
if r1.is_zero() {
|
|
return true;
|
|
}
|
|
n1 = d2;
|
|
n2 = d1;
|
|
d1 = r2;
|
|
d2 = r1;
|
|
}
|
|
}
|
|
|
|
impl<
|
|
Balance: IntegerSquareRoot + Zero + Ord + Add<Balance, Output = Balance>
|
|
+ Mul<Balance, Output = Balance> + Div<Balance, Output = Balance>
|
|
+ Rem<Balance, Output = Balance> + Copy,
|
|
> Approved<Balance> for VoteThreshold {
|
|
fn approved(&self, tally: Tally<Balance>, electorate: Balance) -> bool {
|
|
let sqrt_voters = tally.turnout.integer_sqrt();
|
|
let sqrt_electorate = electorate.integer_sqrt();
|
|
if sqrt_voters.is_zero() { return false; }
|
|
match *self {
|
|
VoteThreshold::SuperMajorityApprove =>
|
|
compare_rationals(tally.nays, sqrt_voters, tally.ayes, sqrt_electorate),
|
|
VoteThreshold::SuperMajorityAgainst =>
|
|
compare_rationals(tally.nays, sqrt_electorate, tally.ayes, sqrt_voters),
|
|
VoteThreshold::SimpleMajority => tally.ayes > tally.nays,
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
|
|
#[test]
|
|
fn should_work() {
|
|
assert!(!VoteThreshold::SuperMajorityApprove.approved(Tally{ayes: 60, nays: 50, turnout: 110}, 210));
|
|
assert!(VoteThreshold::SuperMajorityApprove.approved(Tally{ayes: 100, nays: 50, turnout: 150}, 210));
|
|
}
|
|
}
|