Topologicalsort

[clemens-tolboom]

I've added some more tests. My point of view is tests should help new developers to understand more so I used letters and added more documentation.

I'm not sure why the Algorithm returns Vertices instead of Ids. Is there a reason for this?

The new tests are explicitly written for the
"
the topologic sorting may be non-unique depending on your edges. this
algorithm tries to keep the order of vertices as added to the graph in
this case.
"
which feels 'wrong' as we should not rely on the order.

What do you think?

[clue]

I'm not sure why the Algorithm returns Vertices instead of Ids. Is there a reason for this?

All algorithms operate on object instances instead of IDs, because it's easier to work with and one can easily access the remaining attributes such as IDs.

[..] we should not rely on the order

That's something I've been thinking about as well, but IMHO having a strict order makes things more predictable - and testable. Any thoughts / other suggestions?

Your additional tests look great, thanks for the effort!

[clemens-tolboom]

Maybe I should wait deleting the branch.

Regarding testing I did a in_array head / tail tests:

    $tsl = $graph_object->getTopologicalSortedList();
    $dummy = $tsl;

    $head = array_shift($dummy);
    $this->assertTrue(in_array($head, array('a', 'f', 'p')), "The TSL starts with a, f or p: " . join(', ', $tsl));

    $tail = array_pop($dummy);
    $this->assertTrue(in_array($tail, array('c', 'g', 'q')), "The TSL ends with c, g or q: " . join(', ', $tsl));

Taken from patch http://drupal.org/files/core-graph-1915308-37_1.patch from issue http://drupal.org/node/1915308

BTW you would you generate a big Graph for recursion depth testing. I want to try unwinding the recursion.

[clue]

Your changes have been merged already, so it's safe to delete this branch and/or create a new branch and open a new PR?

Additional tests are always welcome! Your suggestion seems more like an unclean API you're testing against, so maybe we should provide some additional convenience methods?

Regarding generating a bigger graph, just testing it against something like this is likely going to fail if you have the xdebug extension installed:

$length = 1000;
$graph = new Graph();
$last = $graph->createVertex(0);
for ($i = 1; $i <= $length; ++$i) {
    $new = $graph->createVertex($i);
    $last->createEdgeTo($new);
    $last = $new;
}