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[1837] Cannot token by reverse over junction #11600

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ianwilson156 opened this issue Mar 3, 2025 · 2 comments · May be fixed by #11602
Open

[1837] Cannot token by reverse over junction #11600

ianwilson156 opened this issue Mar 3, 2025 · 2 comments · May be fixed by #11602
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1837 rules-broken Game comes to the wrong outcome compared with the rules (fixing these will break games)

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@ianwilson156
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ianwilson156 commented Mar 3, 2025 •
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https://18xx.games/game/199252

BH is running for the first time in OR6.1, it lays a tile in its home (Sarajevo), and it should be able to place a token e.g. in Marburg (reversing over the junction in O19), but the program is skipping the lay token step.

This is a special rule for 1837, that you can token by reversing over a junction. I suspect that this used to work previously.
@ollybh ollybh added rules-broken Game comes to the wrong outcome compared with the rules (fixing these will break games) 1837 and removed needs triage labels Mar 3, 2025
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ollybh commented Mar 3, 2025

BH's turn starts at action 782. The token step is being skipped.

There's definitely code added to 1837 to allow for backtracking when placing tokens. Not sure why it's not working here.

@ollybh ollybh assigned crericha and ollybh and unassigned crericha Mar 3, 2025
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ollybh commented Mar 3, 2025

Got it, the token step isn't using the graph that includes the backtracking.

ollybh added a commit to ollybh/18xx that referenced this issue Mar 3, 2025
@ollybh
[1837] Use backtracking graph in the token step
69ab839 
1837 has two graphs: a standard one and one that allows track to
backtrack at junctions. The latter is needed for placing station tokens,
where this type of route is allowed.

The token step was not using this graph, it was using the standard one.
This meant that not all possible token locations were being included,
and an auto-pass was being generated for the token step if the only
possible token locations involved backtracking.

Fixes tobymao#11600.
@ollybh ollybh linked a pull request Mar 3, 2025 that will close this issue
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[1837] Use backtracking graph in the token step ollybh/18xx
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@ollybh @crericha @ianwilson156