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CommonMark::Iterator(3) User Contributed Perl Documentation CommonMark::Iterator(3)

NAME

CommonMark::Iterator - Iterate CommonMark nodes

SYNOPSIS

    use CommonMark qw(:node :event);
    my $iter = $doc->iterator;
    while (my ($ev_type, $node) = $iter->next) {
        my $node_type = $node->get_type;
        if ($node_type == NODE_PARAGRAPH) {
            if ($ev_type == EVENT_ENTER) {
                print("<p>");
            }
            else {
                print("</p>\n");
            }
        }
        elsif ($node_type == NODE_TEXT) {
            print($node->get_literal);
        }
    }

DESCRIPTION

"CommonMark::Iterator" provides a convenient way to walk through the nodes in a parse tree.

Construction

   my $iterator = $node->iterator;

Creates an iterator from a node. $node is the root node of the iterator.

next

    my $ev_type = $iterator->next;
    my ($ev_type, $node) = $iterator->next;

The contents of the iterator are initially undefined. After the first and each subsequent call to "next", the iterator holds a new event type and a new current node. In scalar context, "next" returns the new event type. In list context, it returns a 2-element list consisting of the new event type and the new current node.

Event types are:

    CommonMark::EVENT_DONE
    CommonMark::EVENT_ENTER
    CommonMark::EVENT_EXIT

Event types can be imported from CommonMark with tag "event".

    use CommonMark qw(:event);

The iterator starts by visiting the root node. Every visited node "V" generates the following sequence of events.

  • Enter the node. The event type is "CommonMark::EVENT_ENTER" and the current node is set to the entered node "V".
  • Visit all children of the node "V" from first to last applying this sequence of events recursively.
  • Except for leaf nodes, exit the node. The event type is "CommonMark::EVENT_EXIT" and the current node is set to the original node "V".

After the root node was exited, the event type is set to "CommonMark::EVENT_DONE" and the current node to "undef". In scalar context, "next" returns "CommonMark::EVENT_DONE". In list context, it returns the empty list.

For leaf nodes, no exit events are generated. Leaf nodes comprise the node types that never have children:

    CommonMark::NODE_HTML
    CommonMark::NODE_HRULE
    CommonMark::NODE_CODE_BLOCK
    CommonMark::NODE_TEXT
    CommonMark::NODE_SOFTBREAK
    CommonMark::NODE_LINEBREAK
    CommonMark::NODE_CODE
    CommonMark::NODE_INLINE_HTML

For other node types, an exit event is generated even if the node has no children.

It is safe to modify nodes after an exit event, or an enter event for leaf nodes. Otherwise, changes to the tree structure can result in undefined behavior.

Accessors

    my $node    = $iter->get_node;
    my $ev_type = $iter->get_event_type;
    my $node    = $iter->get_root;

These accessors return the current node, the current event type, and the root node.

COPYRIGHT

This software is copyright (C) by Nick Wellnhofer.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

2019-07-25 perl v5.40.0