sync with rtgui-0.6

1 files changed, 40 insertions, 0 deletions

diff --git a/components/rtgui/utils/perfect_hash/example-Python/Graph.py b/components/rtgui/utils/perfect_hash/example-Python/Graph.py
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+++ b/components/rtgui/utils/perfect_hash/example-Python/Graph.py
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+#!/usr/bin/env python
+"""
+This example shows how to use the class Graph.
+
+The class implements a graph with 'N' vertices.  First, you connect the
+graph with edges, which have a desired value associated.  Then the vertex
+values are assigned, which will fail if the graph is cyclic.  The vertex
+values are assigned such that the two values corresponding to an edge add
+up to the desired edge value (mod N).
+"""
+import sys
+
+sys.path.append('..')
+from perfect_hash import Graph
+
+G = Graph(3)
+assert G.assign_vertex_values() == True
+    
+# Now we make an edge between vertex 0 and 1 with desired edge value 2:
+G.connect(0, 1, 2)
+
+# Make another edge 1:2 with desired edge value 1:
+G.connect(1, 2, 1)
+    
+# The graph is still acyclic, and assigning values works:
+assert G.assign_vertex_values() == True
+assert G.vertex_values == [0, 2, 2]
+    
+# What do these values mean?
+# When you add the values for edge 0:1 you get 0 + 2 = 2, as desired.
+# For edge 1:2 you add 2 + 2 = 4 = 1 (mod 3), as desired.
+
+# Adding edge 0:2 produces a loop, so the graph is no longer acyclic.
+# Assigning values fails.
+G.connect(0, 2, 0)
+
+assert G.assign_vertex_values() == False
+
+
+print 'OK'