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HVDS / Codex-0.01 / lib / Codex / Deriv.pm 

            

              
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package Codex::Deriv;
use strict;
use Codex::Operator;
my $builtin_equals = Codex::Operator->builtin('equals');
sub new {
        my($proto, $codex, $text) = @_;
        bless {
                'codex' => $codex,
                'text' => $text,
        }, ref($proto) || $proto;
}
sub text { shift->{'text'} }
sub codex { shift->{'codex'} }
sub error {
        my($self, $error) = @_;
        $error .= " in derivation '" . $self->text . "'";
        $self->codex->error($error);
}
sub data {
        my $self = shift;
        $self->{'data'} ||= do {
                my $t = [ split /,\s*/, $self->text ];
                @$t or return $self->error("Couldn't find anything");
                my $d = $self->parse($t, [ 'line' ]);
                if ($d && !$d->[0][0]->builtin) {
                        shift @$d;
                } else {
                        my $rule = $self->codex->lookup->{shift @$t}
                                or return $self->error("Couldn't find a rule");
                        $rule->builtin or return $self->error("Rule isn't a builtin");
                        my $pat = $rule->do_builtin('args')
                                or return $self->error("Couldn't get pattern for rule");
                        $d = $self->parse($t, $pat)
                                or return $self->error("Couldn't get expected args");
                        [ $rule, $d ];
                }
        };
}
sub parse {
        my($self, $text, $pat) = @_;
        return [] if @$text == 0 && @$pat == 0;
        return if @$text < @$pat;
        return unless @$pat;
        my @pat = @$pat;
        my $curpat = shift @pat;
        if (@pat) {
                my($i, $j) = (0, @$text - @pat);
                while ($i++ < $j) {
                        my $d = $self->parse([ @$text[0 .. $i - 1] ], [ $curpat ]);
                        next unless $d;
                        my $e = $self->parse([ @$text[$i .. $#$text] ], \@pat);
                        next unless $e;
                        return [ @$d, @$e ];
                }
                return;
        }
        $text = join ', ', @$text;
        if ($curpat eq 'number') {
                $text =~ /^(-?\d+)$/ or return;
                return [ $1 ];
        } elsif ($curpat eq 'expr') {
                my $e = Codex::Expr->new($self->codex, $text);
                return $e && [ $e ];
        } elsif ($curpat eq 'line') {
                my($line, $vars) = split /:/, $text, 2;
                return unless $line = $self->codex->lookup->{$line};
                return [ [ $line ] ] unless defined $vars;
                my @parts = split /,\s*/, $vars;
                my %vars;
                while (@parts) {
                        my $part = shift @parts;
                        return unless $part =~ s/^(\w+)=//;
                        my $var = $1;
                        my $e = Codex::Expr->new($self->codex, $part);
                        $vars{$var} = $e, next if $e;
                        return unless @parts;
                        $parts[0] = "$var=$part, $parts[0]";
                }
                return [ [ $line, \%vars ] ];
        } else {
                die "panic: unexpected derivation type '$curpat'";
        }
}
sub cpderive {
        my($self, $left, $right) = @_;
        my($lsrc, $largs) = @$left;
        my($rsrc, $rargs) = @$right;
        foreach ($lsrc, $rsrc) {
                next if $_->builtin;
                next unless $self->{'line'};
                next if $self->codex->scope($self->{'line'}, $_, 1);
                $self->codex->error(sprintf "%s out of scope of CP %s", $_->lname, 
                                $self->{'line'}->lname);
        }
        unless ($self->codex->scope($rsrc, $lsrc)) {
                $self->codex->error(sprintf "%s out of scope of %s for CP",
                                $lsrc->lname, $rsrc->lname);
        }
        local $self->{'line'};
        ($self->derive($left), $self->derive($right));
}
sub derive {
        my($self, $data) = @_;
        my($src, $args) = @$data;
        if ($src->builtin) {
                $src->do_builtin('derive', $self, $args);
        } else {
                if ($self->{'line'} && !$self->codex->scope($self->{'line'}, $src)) {
                        $self->codex->error(sprintf "%s out of scope of %s", $src->lname,
                                        $self->{'line'}->lname);
                }
                if ($args) {
                        $src->expr->transform($args);
                } else {
                         $src->expr;
                }
        }
}
sub test {
        my($self, $line) = @_;
        my $data = $self->data or return;
        local $self->{'line'} = $line;
        my $result = $self->derive($data);
        if (!$result) {
                $self->error("Couldn't derive anything");
        } elsif ($line->text ne $result->text) {
                $self->error(sprintf "Derivation '%s' yields '%s'",
                                $line->text, $result->text);
        }
}
1;