X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=appendix-a6.git;a=blobdiff_plain;f=stv;h=68940f452683825259efcecc5fdc2fffbb7c3a38;hp=ba89fce1bfd4dcd359d86f80fe0555820db25cd8;hb=36928c5e0556b62575c7d1a5849834297a678213;hpb=2c0d1b163477f5472ca5f2495f5f436d5205889f

diff --git a/stv b/stv
index ba89fce..68940f4 100755
--- a/stv
+++ b/stv
@@ -20,6 +20,25 @@ use List::MoreUtils qw(nsort_by);
 our $stage=0;
 our @allvotes;
 
+our %tiebreak; # $tiebreak{ winningcand }{ losingcand } = 1
+
+while (@ARGV && $ARGV[0] =~ m/[<>]/) {
+    my ($losers, $winners) = ($? eq '<' ? ($`, $') : ($', $`));
+    my @losers = sort split /\,/, $losers;
+    my @winners = sort split /\,/, $winners;
+    die "@losers @winners" if @losers>1 && @winners>1;
+    my @all = sort @losers, @winners;
+    my $record = sub {
+	my ($how, $howers) = @_;
+	return unless @$howers == 1;
+	die "@all $how" if defined $tiebreak{$how}{"@all"};
+	$tiebreak{$how}{"@all"} = $howers->[0];
+    };
+    $record->('winner', \@winners);
+    $record->('loser',  \@losers);
+    shift @ARGV;
+}    
+
 our $places = shift @ARGV;
 die unless $places eq ($places + 0);
 
@@ -95,27 +114,56 @@ sub equalpiles ($@) {
 
 sub historically_prefer ($@) {
     my ($signum, @choices) = @_;
+    # $signum==+1 means choose candidates with more early preferences
 
     return $choices[0] if @choices < 2;
 
     my $compare = sub {
 	foreach my $sr (@stagerecord) {
-	    my $d = $sr->{ $a->{Cand} } <=> $sr->{ $b->{Cand} };
-	    return $d * $signum if $d;
+	    my $d = ($sr->{ $a->{Cand} }//0) <=> ($sr->{ $b->{Cand} }//0);
+	    return -$d * $signum if $d;
 	}
 	return 0;
     };
 
-    @choices = sort $compare, @choices;
+    @choices = sort $compare @choices;
+
+    print DEBUG "historically_prefer\n",
+	Data::Dumper->Dump([\@choices, \@stagerecord],
+			   [qw(_@choices _@stagerecord)]);
+
+    foreach my $s (@choices) {
+	my $c = $s->{Cand};
+	printf " %6s %10s |", 'tiebrk', $c;
+	foreach my $sr (@stagerecord) {
+	    my $p = pr($sr->{$c} // 0);
+	    $p =~ s/\.0+\b//g;
+	    $p =~ s/ //g;
+	    print "$p|";
+	}
+	print "\n";
+    }
+
     $a = $choices[0];
-    my $numequal = 0;
+    my $numequal = 1;
     for (;;) {
-	last unless $numequal >= @choices;
+	last if $numequal >= @choices;
 	$b = $choices[$numequal];
 	last if $compare->();
+	$numequal++;
+    }
+
+    if ($numequal > 1) {
+	my $how = $signum > 0 ? 'winner' : 'loser';
+        my @all = sort map { $_->{Cand} } @choices[ 0 .. $numequal-1 ];
+	my $hower = $tiebreak{$how}{"@all"};
+	if (defined $hower) {
+	    printf "%7.7s %10s !!!!!!!!!!\n", "TIE".(uc $how), $hower;
+	    return grep { $_->{Cand} eq $hower } @choices;
+	}
+	die "need tie break for $how between @all\n";
     }
 
-    die 'random choice unimplemented' if $numequal > 1;
     return $choices[0];
 }
 
@@ -160,7 +208,7 @@ for (;;) {
     }
     my @sorted;
     my $things_update = sub {
-	foreach my $s (@surpluses, values %sorted) {
+	foreach my $s (values %sorted) {
 	    $s->{Total} = sum0 map { $_->{Weight} } @{ $s->{Votes } };
 	}
 	@sorted = nsort_by { -$_->{Total} } values %sorted;
@@ -203,19 +251,31 @@ for (;;) {
 	my $s = $sorted[0];
 	my $topvoters = $s->{Total};
 	my $surplus = $topvoters - $quota;
-	last unless $surplus > 0;
+	last unless $surplus >= 0;
+	last unless $placesremain;
 
-	printf "%7s %10s ***************\n", 'ELECTED', $s->{Cand};
-	push @elected, $s->{Cand};
+	my @elect = equalpiles 'elect?', @sorted;
 
-	foreach my $vote (@{ $s->{Votes} }) {
-	    votelog $vote, "elected $s->{Cand}";
+	if (@elect > $placesremain) {
+	    # oh my god
+	    @elect = historically_prefer +1, @elect;
+	    printf "%7s %10s\n", 'tie!', $elect[0]{Cand};
 	}
 
-	$s->{Surplus} = $surplus;
-	push @newsurpluses, $s;
-	delete $sorted{ $s->{Cand} };
-	delete $continuing{ $s->{Cand} };
+	foreach $s (@elect) {
+	    printf "%7s %10s ***************\n", 'ELECTED', $s->{Cand};
+	    push @elected, $s->{Cand};
+
+	    foreach my $vote (@{ $s->{Votes} }) {
+		votelog $vote, "elected $s->{Cand}";
+	    }
+
+	    $s->{Surplus} = $surplus;
+	    push @newsurpluses, $s;
+	    delete $sorted{ $s->{Cand} };
+	    delete $continuing{ $s->{Cand} };
+	    $placesremain--;
+	}
 
 	$things_update->();
     }
@@ -234,15 +294,18 @@ for (;;) {
 	    grep { !!voteliveprefs $_ }
 	    @$votes;
 
+	my $derate = 1/1;
 	printf "%7s %10s %s\n", 'xfrable', $s->{Cand}, pr $transferrable;
 	if ($transferrable > $surplus) {
-	    my $derate = $transferrable / $surplus;
+	    $derate = $transferrable / $surplus;
 	    printf "%7s %10s %s\n", 'derate', $s->{Cand}, pr $derate;
 	    foreach my $vote (@{ $s->{Votes} }) {
 		votelog $vote, "part of surplus, derated ". pr $derate;
 		$vote->{Weight} /= $derate;
 	    }
 	}
+	$s->{Total} = $transferrable / $derate;
+
 	push @surpluses, $s;
 
 	$things_update->();