Perlito - misc - tree grammar placeholder

misc/tree_grammar.pl

@@ -0,0 +1,96 @@
+package main {
+    use Data::Dumper;
+    use strict;
+
+    my $in = eval join( '', <> );
+    print Dumper $in;
+
+    my $rule = [ Ref => 'Perlito5::AST::Apply' ];
+    TreeGrammar::scan( $rule, $in );
+
+    $rule = [
+        Lookup => 'name',
+        [ Value => 'a' ]
+    ];
+    TreeGrammar::scan( $rule, $in );
+}
+
+package TreeGrammar {
+    use Data::Dumper;
+    use strict;
+
+    my %dispatch;
+    INIT {
+        %dispatch = (
+            Ref    => \&Ref,       # Ref => 'Perlito5::AST::Apply'
+            Lookup => \&Lookup,    # Lookup => 'namespace'
+            Index  => \&Index,     # Index  => '0'
+            Value  => \&Value,     # Value => '123'
+        );
+    }
+
+    sub render {
+        my ( $rule, $node ) = @_;
+        if ( ref($rule) ) {
+
+            # print "Rule ", Dumper $rule;
+            # print Dumper \%dispatch;
+            return $dispatch{ $rule->[0] }->( $rule, $node );
+        }
+        return;
+    }
+
+    sub scan {
+        my ( $rule, $node ) = @_;
+        render( $rule, $node );
+        if ( ref($node) eq 'ARRAY' ) {
+            scan( $rule, $_ ) for @$node;
+        }
+        elsif ( ref($node) ) {
+            scan( $rule, $_ ) for values %$node;
+        }
+        return;
+    }
+
+    sub Ref {
+        my ( $rule, $node ) = @_;
+        if ( ref($node) eq $rule->[1] ) {
+            print "match: Ref $node\n";
+            return { pos => $node };
+        }
+        return;
+    }
+
+    sub Lookup {
+        my ( $rule, $node ) = @_;
+        return if !ref($node) || ref($node) eq 'ARRAY';
+        if ( exists( $node->{ $rule->[1] } ) ) {
+            print "match: Lookup $node\n";
+            return render( $rule->[2], $node->{ $rule->[1] } ) if $rule->[2];
+            return { pos => $node };
+        }
+        return;
+    }
+
+    sub Index  {
+        my ( $rule, $node ) = @_;
+        return if !ref($node) || ref($node) ne 'ARRAY';
+        if ( exists( $node->[ $rule->[1] ] ) ) {
+            print "match: Index $node\n";
+            return render( $rule->[2], $node->[ $rule->[1] ] ) if $rule->[2];
+            return { pos => $node };
+        }
+        return;
+    }
+
+    sub Value {
+        my ( $rule, $node ) = @_;
+        return if ref($node);
+        if ( $node eq $rule->[1] ) {
+            print "match: Value $node\n";
+            return { pos => $node };
+        }
+        return;
+    }
+
+}