Merge pull request #29 from pradal/traversal

Add traversal algo on graph from container

src/openalea/core/graph/traversal/__init__.py

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+from .tree import pre_order, post_order, level_order
+from .graph import topological_sort, breadth_first_search

src/openalea/core/graph/traversal/graph.py

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+# -*- coding: utf-8 -*-
+# -*- python -*-
+#
+#       OpenAlea.Container
+#
+#       Copyright 2008-2009 INRIA - CIRAD - INRA
+#
+#       File author(s): Christophe Pradal <christophe.pradal.at.cirad.fr>
+#
+#       Distributed under the Cecill-C License.
+#       See accompanying file LICENSE.txt or copy at
+#           http://www.cecill.info/licences/Licence_CeCILL-C_V1-en.html
+#
+#       OpenAlea WebSite : http://openalea.gforge.inria.fr
+#
+###############################################################################
+
+"""
+This module provides several implementation of traversal on a directed graph.
+"""
+
+__license__= "Cecill-C"
+__revision__=" $Id$ "
+
+from collections import deque
+
+def topological_sort(graph, vtx_id, visited = None):
+    '''
+    Topolofgical sort of a directed graph implementing the
+    :class:`openalea.container.interface.graph.IGraph` interface.
+    Return an iterator on the vertices.
+
+    :Parameters:
+        - `graph`: a directed graph
+        - vtx_id: a vertex_identifier
+    
+    .. note :: This is a non recursive implementation.
+    '''
+    if visited is None:
+        visited = {}
+
+    yield vtx_id
+    visited[vtx_id] = True
+    for vid in graph.out_neighbors(vtx_id):
+        if vid in visited:
+            continue
+        for node in topological_sort(graph, vid, visited):
+            yield node
+
+
+def breadth_first_search(graph, vtx_id):
+    '''
+    Breadth first search of a graph implementing the
+    :class:`openalea.container.interface.graph.IGraph` interface.
+    Return an iterator on the vertices.
+
+    :Parameters:
+        - `graph`: a directed graph
+        - vtx_id: a vertex_identifier
+    
+    .. note :: This is a non recursive implementation.
+    '''
+    visited = {}
+
+    queue = deque()
+    queue.append(vtx_id)
+
+    while queue:
+        vid = queue.popleft()
+        if vid in visited:
+            continue
+        yield vid
+        visited[vid] = True
+        queue.extend(graph.out_neighbors(vid))
+

src/openalea/core/graph/traversal/tree.py

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+# -*- coding: utf-8 -*-
+# -*- python -*-
+#
+#       OpenAlea.Container
+#
+#       Copyright 2008-2009 INRIA - CIRAD - INRA
+#
+#       File author(s): Christophe Pradal <christophe.pradal.at.cirad.fr>
+#
+#       Distributed under the Cecill-C License.
+#       See accompanying file LICENSE.txt or copy at
+#           http://www.cecill.info/licences/Licence_CeCILL-C_V1-en.html
+#
+#       OpenAlea WebSite : http://openalea.gforge.inria.fr
+#
+###############################################################################
+
+'''
+This module provides different traversal for tree data structure
+implemented :class:`openalea.container.interface.tree` interface.
+'''
+
+__docformat__ = "restructuredtext"
+__license__ = "Cecill-C"
+__revision__ = " $Id$ "
+
+from collections import deque
+
+def pre_order(tree, vtx_id, edge_type_property = None):
+    '''
+    Traverse a tree in a prefix way.
+    (root then children)
+    Return an iterator on vertices.
+    If an edge_type_property is given, visit first branches rather than successor.
+
+    This is a non recursive implementation.
+    '''
+
+    if edge_type_property is None:
+        yield vtx_id
+        for vid in tree.children(vtx_id):
+            for node in pre_order(tree, vid):
+                yield node
+    else:
+
+        # 1. select first '+' edges
+        successor = []
+        yield vtx_id
+        for vid in tree.children(vtx_id):
+            if edge_type_property.get(vid) == '<':
+                successor.append(vid)
+                continue
+
+            for node in pre_order(tree, vid):
+                yield node
+
+        # 2. select then '<' edges
+        for vid in successor:
+            for node in pre_order(tree, vid):
+                yield node
+
+
+def post_order(tree, vtx_id):
+    '''
+    Traverse a tree in a postfix way.
+    (from leaves to root)
+    '''
+    for vid in tree.children(vtx_id):
+        for node in post_order(tree, vid):
+            yield node
+    yield vtx_id
+
+def level_order(tree, vtx_id):
+    ''' Traverse the vertices in a level order.
+
+    Traverse the root node, then its children and so on.
+    '''
+    queue = deque()
+    queue.append(vtx_id)
+
+    while queue:
+        vid = queue.popleft()
+        yield vid
+        queue.extend(tree.children(vid))
+
+
+def depth_order(tree, vtx_id):
+    '''Traverse all the leaves first.
+    Then their parent until the root.
+
+    .. todo:: To implement
+
+    '''
+    raise NotImplementedError
+
+
+def traverse_tree(tree, vtx_id, visitor):
+    '''
+    Traverse a tree in a prefix or postfix way.
+
+    We call a visitor for each vertex.
+    This is usefull for printing, cmputing or storing vertices
+    in a specific order.
+
+    See boost.graph.
+    '''
+
+    yield visitor.pre_order(vtx_id)
+
+    for v in tree.children(vtx_id):
+        for res in traverse_tree(tree, v, visitor):
+            yield res
+
+    yield visitor.post_order(vtx_id)
+
+
+class Visitor(object):
+    ''' Used during a tree traversal. '''
+
+    def pre_order(self, vtx_id):
+        pass
+
+    def post_order(self, vtx_id):
+        pass