Implement ERS76 rules

docs/options.md

@@ -14,7 +14,8 @@ The preset dropdown allows you to choose from a hardcoded list of preloaded STV
 * [*Wright STV*](https://www.aph.gov.au/Parliamentary_Business/Committees/House_of_Representatives_Committees?url=em/elect07/subs/sub051.1.pdf): Rules proposed by Anthony van der Craats designed for computer counting, involving reset and re-iteration of the count after each candidate exclusion. Validated against the [EVE Online reference implementation](https://github.com/ccpgames/ccp-wright-stv) for the [CSM 15 election](https://www.eveonline.com/news/view/meet-the-new-council).
 * [*PRSA 1977*](https://www.prsa.org.au/rule1977.htm): Simple rules designed for hand counting, using the exclusive Gregory method, with counting automatically performed in thousandths of a vote. Validated against [example 1](https://www.prsa.org.au/example1.pdf) of the PRSA's [*Proportional Representation Manual*](https://www.prsa.org.au/publicat.htm#p2).
 * [*ERS97*](https://www.electoral-reform.org.uk/latest-news-and-research/publications/how-to-conduct-an-election-by-the-single-transferable-vote-3rd-edition/): More complex rules designed for hand counting, using the exclusive Gregory method. Validated against the ERS97 model election.
-	* *ERS73*: Former rules from the 1973 1st edition. The quota is calculated always to 2 decimal places – for full ERS73 compliance, set *Round quota to 0 d.p.* when the quota is 100 or more.
+	* *ERS76*: Former rules from the 1976 2nd edition. The quota is always calculated to 2 decimal places – for full ERS76 compliance, set *Round quota to 0 d.p.* when the quota is more than 100.
+	* *ERS73*: Former rules from the 1973 1st edition. The quota is always calculated to 2 decimal places – for full ERS73 compliance, set *Round quota to 0 d.p.* when the quota is 100 or more.
 
 This functionality is not available on the command line.
 

html/index.html

@@ -44,6 +44,7 @@
 						<option value="wright">Wright STV</option>
 						<option value="prsa77">PRSA 1977</option>
 						<option value="ers97">ERS97</option>
+						<option value="ers76">ERS76</option>
 						<option value="ers73">ERS73</option>
 					</select>
 				</label>
@@ -79,6 +80,7 @@
 								<option value="static" selected>Static quota</option>
 								<!--<option value="progressive">Progressive quota</option>-->
 								<option value="ers97">Static with ERS97 rules</option>
+								<option value="ers76">Static with ERS76 rules</option>
 							</select>
 						</label>
 					</div>

html/index.js

@@ -548,6 +548,31 @@ function changePreset() {
 		document.getElementById('selPapers').value = 'transferable';
 		document.getElementById('selExclusion').value = 'by_value';
 		document.getElementById('selTies').value = 'forwards,random';
+	} else if (document.getElementById('selPreset').value === 'ers76') {
+		document.getElementById('selQuotaCriterion').value = 'geq';
+		document.getElementById('selQuota').value = 'droop_exact';
+		document.getElementById('selQuotaMode').value = 'ers76';
+		document.getElementById('chkBulkElection').checked = true;
+		document.getElementById('chkBulkExclusion').checked = true;
+		document.getElementById('chkDeferSurpluses').checked = true;
+		document.getElementById('selNumbers').value = 'fixed';
+		document.getElementById('txtDP').value = '5';
+		document.getElementById('txtPPDP').value = '2';
+		document.getElementById('chkNormaliseBallots').checked = false;
+		document.getElementById('chkRoundQuota').checked = true;
+		document.getElementById('txtRoundQuota').value = '2';
+		document.getElementById('chkRoundVotes').checked = true;
+		document.getElementById('txtRoundVotes').value = '2';
+		document.getElementById('chkRoundTVs').checked = true;
+		document.getElementById('txtRoundTVs').value = '2';
+		document.getElementById('chkRoundWeights').checked = true;
+		document.getElementById('txtRoundWeights').value = '2';
+		document.getElementById('selSumTransfers').value = 'single_step';
+		document.getElementById('selSurplus').value = 'by_size';
+		document.getElementById('selTransfers').value = 'eg';
+		document.getElementById('selPapers').value = 'transferable';
+		document.getElementById('selExclusion').value = 'by_value';
+		document.getElementById('selTies').value = 'forwards,random';
 	} else if (document.getElementById('selPreset').value === 'ers73') {
 		document.getElementById('selQuotaCriterion').value = 'geq';
 		document.getElementById('selQuota').value = 'droop_exact';

src/main.rs

@@ -104,7 +104,7 @@ struct STV {
 	quota_criterion: String,
 	
 	/// Whether to apply a form of progressive quota
-	#[clap(help_heading=Some("QUOTA"), long, possible_values=&["static", "ers97"], default_value="static", value_name="mode")]
+	#[clap(help_heading=Some("QUOTA"), long, possible_values=&["static", "ers97", "ers76"], default_value="static", value_name="mode")]
 	quota_mode: String,
 	
 	// ------------------

src/stv/mod.rs

@@ -144,6 +144,7 @@ impl STVOptions {
 			quota_mode: match quota_mode {
 				"static" => QuotaMode::Static,
 				"ers97" => QuotaMode::ERS97,
+				"ers76" => QuotaMode::ERS76,
 				_ => panic!("Invalid --quota-mode"),
 			},
 			ties: ties.into_iter().map(|t| match t.as_str() {
@@ -315,6 +316,8 @@ pub enum QuotaMode {
 	Static,
 	/// Static quota with ERS97 rules
 	ERS97,
+	/// Static quota with ERS76 rules
+	ERS76,
 }
 
 impl QuotaMode {
@@ -323,6 +326,7 @@ impl QuotaMode {
 		match self {
 			QuotaMode::Static => "--quota-mode static",
 			QuotaMode::ERS97 => "--quota-mode ers97",
+			QuotaMode::ERS76 => "--quota-mode ers76",
 		}.to_string()
 	}
 }
@@ -664,8 +668,8 @@ fn calculate_quota<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
 		state.logger.log_literal(log);
 	}
 	
-	if let QuotaMode::ERS97 = opts.quota_mode {
+	if opts.quota_mode == QuotaMode::ERS97 || opts.quota_mode == QuotaMode::ERS76 {
-		// ERS97 rules
+		// ERS97/ERS76 rules
 		
 		// -------------------------
 		// Reduce quota if allowable
@@ -722,7 +726,7 @@ fn calculate_quota<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
 			}
 		}
 	} else {
-		// No ERS97 rules
+		// No ERS97/ERS76 rules
 		if state.vote_required_election.is_none() || opts.surplus == SurplusMethod::Meek {
 			state.vote_required_election = state.quota.clone();
 		}
@@ -789,10 +793,9 @@ fn elect_meeting_quota<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVO
 		
 		if opts.quota_mode == QuotaMode::ERS97 {
 			// Vote required for election may have changed
+			// This is not performed in ERS76 - TODO: Check this
 			calculate_quota(state, opts);
-		}
 			
-		if opts.quota_mode == QuotaMode::ERS97 {
 			// Repeat in case vote required for election has changed
 			match elect_meeting_quota(state, opts) {
 				Ok(_) => {}

src/stv/wasm.rs

@@ -292,7 +292,7 @@ fn init_results_table<N: Number>(election: &Election<N>, opts: &stv::STVOptions)
 		result.push_str(&format!(r#"<tr class="candidate transfers"><td rowspan="2">{}</td></tr><tr class="candidate votes"></tr>"#, candidate.name));
 	}
 	result.push_str(r#"<tr class="info transfers"><td rowspan="2">Exhausted</td></tr><tr class="info votes"></tr><tr class="info transfers"><td rowspan="2">Loss by fraction</td></tr><tr class="info votes"></tr><tr class="info transfers"><td>Total</td></tr><tr class="info transfers"><td>Quota</td></tr>"#);
-	if opts.quota_mode == stv::QuotaMode::ERS97 {
+	if opts.quota_mode == stv::QuotaMode::ERS97 || opts.quota_mode == stv::QuotaMode::ERS76 {
 		result.push_str(r#"<tr class="info transfers"><td>Vote required for election</td></tr>"#);
 	}
 	return result;
@@ -354,7 +354,7 @@ fn update_results_table<N: Number>(stage_num: usize, state: &CountState<N>, opts
 	result.push(&format!(r#"<td class="{}count">{}</td>"#, tdclasses2, pp(&total_vote, opts.pp_decimals)).into());
 	
 	result.push(&format!(r#"<td class="{}count">{}</td>"#, tdclasses2, pp(state.quota.as_ref().unwrap(), opts.pp_decimals)).into());
-	if opts.quota_mode == stv::QuotaMode::ERS97 {
+	if opts.quota_mode == stv::QuotaMode::ERS97 || opts.quota_mode == stv::QuotaMode::ERS76 {
 		result.push(&format!(r#"<td class="{}count">{}</td>"#, tdclasses2, pp(state.vote_required_election.as_ref().unwrap(), opts.pp_decimals)).into());
 	}