#!/usr/bin/perl -w
use strict;

sub UNK() { 0; }
sub LTE() { 1; }
sub GTE() { 2; }
sub EQU() { 3; }
my $Pref= {};
my %OpBits= (
    '<' => LTE(),
    '>' => GTE(),
    '=' => EQU(),
);
my %RevBits= (
    UNK() => UNK(),
    LTE() => GTE(),
    GTE() => LTE(),
    EQU() => EQU(),
);

Main( @ARGV );
exit( 0 );


sub onePref
{
    my( $x, $bits, $y )= @_;
    return
        if  $bits == UNK();
    if(  $Pref->{$x}  &&  exists $Pref->{$x}{$y}  ) {
        die "ERROR contradictory $x $y\n"
            if  $Pref->{$x}{$y} != $bits;
    } else {
        $Pref->{$x}{$y}= $bits;
        $Pref->{$y}{$x}= $RevBits{$bits};
    }
}

sub allPrefs
{
    my( $x, $c, $y )= @_;
    my $bits= $OpBits{$c};
    $Pref->{$x}{$x}= $Pref->{$y}{$y}= EQU();
    onePref( $x, $bits, $y );
    while(  my($z,$v)= each %{$Pref->{$y}}  ) {
        onePref( $x, $bits & $v, $z );
    }
    $bits= $RevBits{$bits};
    while(  my($z,$v)= each %{$Pref->{$x}}  ) {
        onePref( $y, $bits & $v, $z );
    }
}

sub partialOrder
{
    for my $chain (  @_  ) {
        while(  $chain =~ /\G\s*(\w+)\s*([<=>])\s*(?=(\w+))/gc  ) {
            my( $x, $c, $y )= ( $1, $2, $3 );
            allPrefs( $x, $c, $y );
        }
        if(  $chain !~ /\G\s*(\w+)\s*$/g  ) {
            die "Invalid preferences ($chain).\n";
        }
    }
}

sub compare
{
    my( $x, $y )= @_;
    return $Pref->{$x}{$y} || UNK();
}

sub Main
{
    partialOrder(
        'xx < yy < zz > aa',
        'bb < yy = aa > cc',
    );

    my @vals= sort keys %$Pref;
    my %bitVal= (
        UNK() => '.',
        LTE() => '-',
        GTE() => '+',
        EQU() => '=',
    );
    my $len= 1;
    for(  map length($_), @vals  ) {
        $len= $_
            if  $len < $_;
    }
    for my $v (  @vals  ) {
        $v= sprintf "%-*s", $len, $v;
    }

    print "Comparison Table:\n";
    print join " ", ' 'x$len, @vals;
    print $/;
    for my $x (  @vals  ) {
        print "$x ";
        for my $y (  @vals  ) {
            my $c= compare( $x, $y );
            printf "%-*s", 1+$len, $bitVal{$c};
        }
        print "\n";
    }

    partialOrder( 'ww < ww' );
}