Show loss by fraction, and implement --sort-votes and --hide-excluded

src/election.rs

@@ -91,6 +91,7 @@ pub struct CountState<'a, N> {
 	
 	pub candidates: HashMap<&'a Candidate, CountCard<'a, N>>,
 	pub exhausted: CountCard<'a, N>,
+	pub loss_fraction: CountCard<'a, N>,
 	
 	pub quota: N,
 	
@@ -104,6 +105,7 @@ impl<'a, N: Number> CountState<'a, N> {
 			election: &election,
 			candidates: HashMap::new(),
 			exhausted: CountCard::new(),
+			loss_fraction: CountCard::new(),
 			quota: N::new(),
 			num_elected: 0,
 			num_excluded: 0,
@@ -121,6 +123,7 @@ impl<'a, N: Number> CountState<'a, N> {
 			count_card.step();
 		}
 		self.exhausted.step();
+		self.loss_fraction.step();
 	}
 }
 

src/main.rs

@@ -19,7 +19,7 @@ mod election;
 mod numbers;
 mod stv;
 
-use crate::election::{CandidateState, CountState, CountStateOrRef, Election, StageResult};
+use crate::election::{Candidate, CandidateState, CountCard, CountState, CountStateOrRef, Election, StageResult};
 use crate::numbers::{Number, NumType};
 
 use clap::Clap;
@@ -48,33 +48,60 @@ enum Command {
 struct STV {
 	/// Path to the BLT file to be counted
 	filename: String,
+	/// Hide excluded candidates from results report
+	#[clap(long)]
+	hide_excluded: bool,
+	/// Sort candidates by votes in results report
+	#[clap(long)]
+	sort_votes: bool,
 	/// Print votes to specified decimal places in results report
 	#[clap(long, default_value="2")]
 	pp_decimals: usize,
 }
 
-fn print_stage<N: Number>(stage_num: usize, result: &StageResult<N>, cmd_opts: &STV) {
+fn print_candidates<'a, N: 'a + Number, I: Iterator<Item=(&'a Candidate, &'a CountCard<'a, N>)>>(candidates: I, cmd_opts: &STV) {
-	println!("{}. {}", stage_num, result.title);
-	println!("{}", result.logs.join(" "));
-	
-	// Sort candidates
-	//let mut candidates: Vec<(&&Candidate, &CountCard<N>)> = result.state.candidates.iter().collect();
-	//candidates.sort_unstable_by(|a, b| a.1.votes.partial_cmp(&b.1.votes).unwrap());
-	let candidates = result.state.as_ref().election.candidates.iter().map(|c| (c, result.state.as_ref().candidates.get(c).unwrap()));
-	
-	// Print candidates
-	//for (candidate, count_card) in candidates.into_iter().rev() {
 	for (candidate, count_card) in candidates {
 		if count_card.state == CandidateState::ELECTED {
 			println!("- {}: {:.dps$} ({:.dps$}) - ELECTED {}", candidate.name, count_card.votes, count_card.transfers, count_card.order_elected, dps=cmd_opts.pp_decimals);
 		} else if count_card.state == CandidateState::EXCLUDED {
-			println!("- {}: {:.dps$} ({:.dps$}) - Excluded {}", candidate.name, count_card.votes, count_card.transfers, -count_card.order_elected, dps=cmd_opts.pp_decimals);
+			// If --hide-excluded, hide unless nonzero votes or nonzero transfers
+			if !cmd_opts.hide_excluded || !count_card.votes.is_zero() || !count_card.transfers.is_zero() {
+				println!("- {}: {:.dps$} ({:.dps$}) - Excluded {}", candidate.name, count_card.votes, count_card.transfers, -count_card.order_elected, dps=cmd_opts.pp_decimals);
+			}
 		} else {
 			println!("- {}: {:.dps$} ({:.dps$})", candidate.name, count_card.votes, count_card.transfers, dps=cmd_opts.pp_decimals);
 		}
 	}
+}
+
+fn print_stage<N: Number>(stage_num: usize, result: &StageResult<N>, cmd_opts: &STV) {
+	// Print stage details
+	println!("{}. {}", stage_num, result.title);
+	println!("{}", result.logs.join(" "));
 	
-	println!("Quota: {:.dps$}", result.state.as_ref().quota, dps=cmd_opts.pp_decimals);
+	let state = result.state.as_ref();
+	
+	// Print candidates
+	if cmd_opts.sort_votes {
+		// Sort by votes if requested
+		let mut candidates: Vec<(&Candidate, &CountCard<N>)> = state.candidates.iter()
+			.map(|(c, cc)| (*c, cc)).collect();
+		// First sort by order of election (as a tie-breaker, if votes are equal)
+		candidates.sort_unstable_by(|a, b| b.1.order_elected.partial_cmp(&a.1.order_elected).unwrap());
+		// Then sort by votes
+		candidates.sort_by(|a, b| a.1.votes.partial_cmp(&b.1.votes).unwrap());
+		print_candidates(candidates.into_iter().rev(), cmd_opts);
+	} else {
+		let candidates = state.election.candidates.iter()
+			.map(|c| (c, state.candidates.get(c).unwrap()));
+		print_candidates(candidates, cmd_opts);
+	}
+	
+	// Print summary rows
+	println!("Exhausted: {:.dps$} ({:.dps$})", state.exhausted.votes, state.exhausted.transfers, dps=cmd_opts.pp_decimals);
+	println!("Loss by fraction: {:.dps$} ({:.dps$})", state.loss_fraction.votes, state.loss_fraction.transfers, dps=cmd_opts.pp_decimals);
+	
+	println!("Quota: {:.dps$}", state.quota, dps=cmd_opts.pp_decimals);
 	
 	println!("");
 }

src/numbers.rs

@@ -190,9 +190,7 @@ impl ops::AddAssign for Rational {
 }
 
 impl ops::SubAssign for Rational {
-	fn sub_assign(&mut self, _rhs: Self) {
+	fn sub_assign(&mut self, rhs: Self) { self.0 -= rhs.0 }
-		todo!()
-	}
 }
 
 impl ops::MulAssign for Rational {
@@ -214,15 +212,11 @@ impl ops::RemAssign for Rational {
 }
 
 impl ops::AddAssign<&Rational> for Rational {
-	fn add_assign(&mut self, rhs: &Rational) {
+	fn add_assign(&mut self, rhs: &Rational) { self.0 += &rhs.0 }
-		self.0 += &rhs.0;
-	}
 }
 
 impl ops::SubAssign<&Rational> for Rational {
-	fn sub_assign(&mut self, _rhs: &Rational) {
+	fn sub_assign(&mut self, rhs: &Rational) { self.0 -= &rhs.0 }
-		todo!()
-	}
 }
 
 impl ops::MulAssign<&Rational> for Rational {
@@ -243,6 +237,11 @@ impl ops::RemAssign<&Rational> for Rational {
 	}
 }
 
+impl ops::Neg for &Rational {
+	type Output = Rational;
+	fn neg(self) -> Self::Output { Rational(rug::Rational::from(-&self.0)) }
+}
+
 impl ops::Add<&Rational> for &Rational {
 	type Output = Rational;
 	fn add(self, _rhs: &Rational) -> Self::Output {

src/stv/mod.rs

@@ -21,7 +21,7 @@ use crate::numbers::Number;
 use crate::election::{Candidate, CandidateState, CountCard, CountState, Parcel, Vote};
 
 use std::collections::HashMap;
-use std::ops::Sub;
+use std::ops::{Neg, Sub};
 
 struct NextPreferencesResult<'a, N> {
 	candidates: HashMap<&'a Candidate, NextPreferencesEntry<'a, N>>,
@@ -148,7 +148,11 @@ pub fn elect_meeting_quota<N: Number>(state: &mut CountState<N>) {
 	}
 }
 
-pub fn distribute_surpluses<N: Number>(state: &mut CountState<N>) -> bool where for<'r> &'r N: Sub<&'r N, Output=N> {
+pub fn distribute_surpluses<N: Number>(state: &mut CountState<N>) -> bool
+where
+	for<'r> &'r N: Sub<&'r N, Output=N>,
+	for<'r> &'r N: Neg<Output=N>
+{
 	let mut has_surplus: Vec<(&&Candidate, &CountCard<N>)> = state.candidates.iter()
 		.filter(|(_, cc)| cc.votes > state.quota)
 		.collect();
@@ -167,7 +171,11 @@ pub fn distribute_surpluses<N: Number>(state: &mut CountState<N>) -> bool where
 	return false;
 }
 
-fn distribute_surplus<N: Number>(state: &mut CountState<N>, elected_candidate: &Candidate) where for<'r> &'r N: Sub<&'r N, Output=N> {
+fn distribute_surplus<N: Number>(state: &mut CountState<N>, elected_candidate: &Candidate)
+where
+	for<'r> &'r N: Sub<&'r N, Output=N>,
+	for<'r> &'r N: Neg<Output=N>
+{
 	let count_card = state.candidates.get(elected_candidate).unwrap();
 	let surplus = &count_card.votes - &state.quota;
 	
@@ -181,35 +189,47 @@ fn distribute_surplus<N: Number>(state: &mut CountState<N>, elected_candidate: &
 	// Transfer candidate votes
 	// Unweighted inclusive Gregory
 	// TODO: Other methods
-	let transfer_value = surplus.clone() / &result.total_ballots;
+	//let transfer_value = surplus.clone() / &result.total_ballots;
+	let mut checksum = N::new();
 	
 	for (candidate, entry) in result.candidates.into_iter() {
 		let mut parcel = entry.votes as Parcel<N>;
 		
 		// Reweight votes
 		for vote in parcel.iter_mut() {
-			vote.value = vote.ballot.orig_value.clone() * &transfer_value;
+			//vote.value = vote.ballot.orig_value.clone() * &transfer_value;
+			vote.value = vote.ballot.orig_value.clone() * &surplus / &result.total_ballots;
 		}
 		
 		let count_card = state.candidates.get_mut(candidate).unwrap();
 		count_card.parcels.push(parcel);
 		
-		let mut total_transferred = entry.num_ballots * &surplus / &result.total_ballots;
+		let mut candidate_transfers = entry.num_ballots * &surplus / &result.total_ballots;
 		// Round transfers
 		// TODO: Make configurable
-		total_transferred.floor_mut();
+		candidate_transfers.floor_mut();
-		count_card.transfer(&total_transferred);
+		count_card.transfer(&candidate_transfers);
+		checksum += candidate_transfers;
 	}
 	
 	// Transfer exhausted votes
 	let parcel = result.exhausted.votes as Parcel<N>;
 	state.exhausted.parcels.push(parcel);
-	state.exhausted.transfer(&result.exhausted.num_votes);
+	
+	let mut exhausted_transfers = result.exhausted.num_ballots * &surplus / &result.total_ballots;
+	// TODO: Make configurable
+	exhausted_transfers.floor_mut();
+	state.exhausted.transfer(&exhausted_transfers);
+	checksum += exhausted_transfers;
 	
 	// Finalise candidate votes
 	let count_card = state.candidates.get_mut(elected_candidate).unwrap();
-	count_card.transfers = -surplus;
+	count_card.transfers = -&surplus;
 	count_card.votes.assign(&state.quota);
+	checksum -= surplus;
+	
+	// Update loss by fraction
+	state.loss_fraction.transfer(&-checksum);
 }
 
 pub fn bulk_elect<N: Number>(state: &mut CountState<N>) -> bool {
@@ -278,23 +298,39 @@ fn exclude_candidate<N: Number>(state: &mut CountState<N>, excluded_candidate: &
 	let result = next_preferences(state, votes);
 	
 	// Transfer candidate votes
+	let mut checksum = N::new();
+	
 	for (candidate, entry) in result.candidates.into_iter() {
 		let parcel = entry.votes as Parcel<N>;
 		let count_card = state.candidates.get_mut(candidate).unwrap();
 		count_card.parcels.push(parcel);
 		
-		count_card.transfer(&entry.num_votes);
+		// Round transfers
+		// TODO: Make configurable
+		let mut candidate_transfers = entry.num_votes;
+		candidate_transfers.floor_mut();
+		count_card.transfer(&candidate_transfers);
+		checksum += candidate_transfers;
 	}
 	
 	// Transfer exhausted votes
 	let parcel = result.exhausted.votes as Parcel<N>;
 	state.exhausted.parcels.push(parcel);
-	state.exhausted.transfer(&result.exhausted.num_votes);
+	
+	let mut exhausted_transfers = result.exhausted.num_votes;
+	// TODO: Make configurable
+	exhausted_transfers.floor_mut();
+	state.exhausted.transfer(&exhausted_transfers);
+	checksum += exhausted_transfers;
 	
 	// Finalise candidate votes
 	let count_card = state.candidates.get_mut(excluded_candidate).unwrap();
+	checksum -= &count_card.votes;
 	count_card.transfers = -count_card.votes.clone();
 	count_card.votes = N::new();
+	
+	// Update loss by fraction
+	state.loss_fraction.transfer(&-checksum);
 }
 
 pub fn finished_before_stage<N: Number>(state: &CountState<N>) -> bool {