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Re^2: how to construct tree from parent pointer list

by bryank (Acolyte)
on Jun 30, 2009 at 13:30 UTC ( #776023=note: print w/replies, xml ) Need Help??


in reply to Re: how to construct tree from parent pointer list
in thread how to construct tree from parent pointer list

Hi,

How do you output the tree? I tried using the various Tree methods with the keys of the hash, but without success.

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Re^3: how to construct tree from parent pointer list
by ikegami (Pope) on Jun 30, 2009 at 13:59 UTC
    Like any other tree.
    sub visit_preorder { my ($cb, node, $depth) = @_; $depth ||= 0; $cb->($node, $depth); visit_preorder($cb, $_, $depth+1) for $node->children(); } sub visit_postorder { my ($cb, $node, $depth) = @_; $depth ||= 0; visit_postorder($cb, $_, $depth+1) for $node->children(); $cb->($node, $depth); } visit_preorder(sub { my ($node, $depth) = @_; ... }, $root);

    It's odd that the module doesn't provide this for you.

    What's wrong with the solutions we've already customised for you?

      Thanks. The module does provide an example for output, but I couldn't figure out how to implement it in the example shown here. For example, here is what the module gives:

      my @nodes = $tree->traverse( $tree->PRE_ORDER );
      The example I was working off of:

      use Tree (); my %nodes; while (<>) { my ($child, $parent) = split /:/; my $parent_node = $nodes{$parent} ||= Tree->new($parent); my $child_node = $nodes{$child} ||= Tree->new($child); $parent_node->add_child($child_node); } my @roots = grep { $_->is_root } values %nodes; die("Invalid data: Multiple roots\n") if @roots > 1; my $root = $roots[0];

      Basically, I didn't know what to do since I couldn't find a tree object? I'm sure I am missing all sorts of obvious signs in the code -- I am just too much of a newby to fully understand it. Sorry.

        The module does provide an example for output,

        The module's traverse is useless in most circumstances since it provides a flat list.

        Basically, I didn't know what to do since I couldn't find a tree object?

        Every node is a Tree object.

      Hi, Can you explain what the pieces of this does

      sub visit_preorder { my ($cb, node, $depth) = @_; $depth ||= 0; $cb->($node, $depth); visit_preorder($cb, $_, $depth+1) for $node->children(); }

      For example, what is '$cb' ? What I am trying to do is output the tree in a flattened format once the tree is built. Something like : Fruit|Apple|Granny Smith.. Fruit being the parent of Apple, Apple being the parent of Granny Smith..

        For example, what is '$cb'

        The first argument. It's expected to be a code reference.

        What I am trying to do is output the tree in a flattened format once the tree is built.

        Based on the code from Re: Tree path analyzer regex problem (maybe other issues)?, a reply in an older thread of yours,

        sub leaves { my $node = shift; my @children = $node->children(); if (!@children) { print(join('|', @_), "\n"); } else { for my $child (@children) { leaves($child, @_, $child->value()); } } }

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