array: avoid crash on unset variable

[jimtcl.git] / tree.tcl

# Conceptually compatible with tcllib ::struct::tree
# but uses an object based interface.
# To mimic tcllib, do:
#   rename [tree] mytree

package require oo

# set pt [tree]
#
#   Create a tree
#   This automatically creates a node named "root"
#
# $pt destroy
#
#   Destroy the tree and all it's nodes
#
# $pt set <nodename> <key> <value>
#
#   Set the value for the given key
#
# $pt lappend <nodename> <key> <value> ...
#
#   Append to the (list) value(s) for the given key, or set if not yet set
#
# $pt keyexists <nodename> <key>
#
#   Returns 1 if the given key exists
#
# $pt get <nodename> <key>
#
#   Returns the value associated with the given key
#
# $pt getall <nodename>
#
#   Returns the entire attribute dictionary associated with the given key
#
# $pt depth <nodename>
#
#   Returns the depth of the given node. The depth of "root" is 0.
#
# $pt parent <nodename>
#
#   Returns the name of the parent node, or "" for the root node.
#
# $pt numchildren <nodename>
#
#   Returns the number of child nodes.
#
# $pt children <nodename>
#
#   Returns a list of the child nodes.
#
# $pt next <nodename>
#
#   Returns the next sibling node, or "" if none.
#
# $pt insert <nodename> ?index?
#
#   Add a new child node to the given node.
#   THe default index is "end"
#   Returns the name of the newly added node
#
# $pt walk <nodename> dfs|bfs {actionvar nodevar} <code>
#
#   Walks the tree starting from the given node, either breadth first (bfs)
#   depth first (dfs).
#   The value "enter" or "exit" is stored in variable $actionvar
#   The name of each node is stored in $nodevar.
#   The script $code is evaluated twice for each node, on entry and exit.
#
# $pt dump
#
#   Dumps the tree contents to stdout

#------------------------------------------
# Internal implementation.
# The tree class has 4 instance variables.
# - tree is a dictionary. key=node, value=node value dictionary
# - parent is a dictionary. key=node, value=parent of this node
# - children is a dictionary. key=node, value=list of child nodes for this node
# - nodeid is an integer which increments to give each node a unique id

# Construct a tree with a single root node with no parent and no children
class tree {
        tree {root {}}
        parents {root {}}
        children {root {}}
        nodeid 0
}

# Simply walk up the tree to get the depth
tree method depth {node} {
        set depth 0
        while {$node ne "root"} {
                incr depth
                set node [dict get $parents $node]
        }
        return $depth
}

tree method parent {node} {
        dict get $parents $node
}

tree method children {node} {
        dict get $children $node
}

tree method numchildren {node} {
        llength [dict get $children $node]
}

tree method next {node} {
        # My siblings are my parents children
        set siblings [dict get $children [dict get $parents $node]]
        # Find me
        set i [lsearch $siblings $node]
        incr i
        lindex $siblings $i
}

tree method set {node key value} {
        dict set tree $node $key $value
        return $value
}

tree method get {node key} {
        dict get $tree $node $key
}

tree method keyexists {node key} {
        dict exists $tree $node $key
}

tree method getall {node} {
        dict get $tree $node
}

tree method insert {node {index end}} {

        # Make a new node and add it to the tree
        set childname node[incr nodeid]
        dict set tree $childname {}

        # The new node has no children
        dict set children $childname {}

        # Set the parent
        dict set parents $childname $node

        # And add it as a child
        set nodes [dict get $children $node]
        dict set children $node [linsert $nodes $index $childname]

        return $childname
}

tree method lappend {node key args} {
        if {[dict exists $tree $node $key]} {
                set result [dict get $tree $node $key]
        }
        lappend result {*}$args
        dict set tree $node $key $result
        return $result
}

# $tree walk node bfs|dfs {action loopvar} <code>
#
tree method walk {node type vars code} {
        # set up vars
        lassign $vars actionvar namevar

        set n $node

        if {$type ne "child"} {
                upvar 2 $namevar name $actionvar action

                # Enter this node
                set name $node
                set action enter

                uplevel 2 $code
        }

        if {$type eq "dfs"} {
                # Depth-first so do the children
                foreach child [$self children $n] {
                        uplevel 2 [list $self walk $child $type $vars $code]
                }
        } elseif {$type ne "none"} {
                # Breadth-first so do the children to one level only
                foreach child [$self children $n] {
                        uplevel 2 [list $self walk $child none $vars $code]
                }

                # Now our grandchildren
                foreach child [$self children $n] {
                        uplevel 2 [list $self walk $child child $vars $code]
                }
        }

        if {$type ne "child"} {
                # Exit this node
                set name $node
                set action exit

                uplevel 2 $code
        }
}

tree method dump {} {
        $self walk root dfs {action n} {
                set indent [string repeat "  " [$self depth $n]]
                if {$action eq "enter"} {
                        puts "$indent$n ([$self getall $n])"
                }
        }
        puts ""
}