def test_false(self):
     x = 'A'
     trie = graph.Graph()
     trie.node('A')
     trie.node('B')
     trie.edge('f', 'A', 'B', 'c')
     val = trie_methods.arrived(x, trie)
     self.assertFalse(val)
 def test_normal(self):
     x = 'B'
     trie = graph.Graph()
     trie.node('A')
     trie.node('B')
     trie.edge('f', 'A', 'B', 'c')
     val = trie_methods.arrived(x, trie)
     self.assertTrue(val)
def is_prefix(text, trie):

    # is_prefix determines whether a given text, starting from the text's
    # first character, matches a branch of
    # the given trie, and is thus one of the patterns from which
    # the trie was constructed.

    if not (isinstance(text, str) or isinstance(trie, graph.Graph)):
        raise TypeError('ERROR: is_prefix requires string and trie.')
    else:

        # set the current node to the root of the trie.
        x = trie_methods.root(trie)

        # add an extra space at the end of the text to ensure the algorithm
        # runs to completion and identifies when it has arrived at a leaf.
        text = text + ' '

        # iterate through the symbols in the text.
        for s in text:
            # if the current node has arrived at a leaf,
            # then a pattern matches this text.
            if trie_methods.arrived(x, trie):
                return True

            # if the current node has not arrived at a leaf,
            # but an edge exists matching
            # the current symbol, select that edge and travel to
            # that edge's codomain.
            elif trie_methods.edge_exists(s, x, trie):
                e = trie_methods.select(s, x, trie)
                x = trie.cod[e]
            else:
                # if no such edge exists, the current text
                # does not match any pattern.
                return False