Re: [Rails-devel] revenue library

[alexti <al...@sh...>]

On Wed, 19 May 2010 14:42:10 -0600, Stefan Frey (web.de)  
<ste...@we...> wrote:

> Erik:
> yes you are right:
>
> The city location vertex set rule does not cover cases below.
> And you are right again that (any of) your suggested rule(s) would cover  
> the
> Berlin tile as well.
>
> However there is some reason why I was reluctant to implement your rule:
> The main issue is that is difficult to define the rule first and then to
> transfer it to the vertex graph.
>
> To cut that short:
> 1) Is the rule "only one city on a hex can be visited" (and does this  
> mean
> city or any kind of station?) or "if a train has left any hex,it may not
> reenter that same hex".
>
> 2) Especially the implementation of the latter defintion is particularly  
> hard
> to convert into the vertex structure: If I define all side vertexes as a
> vertex set, a train will never be able to leave the hex again. Most  
> likely
> this requires the addition of additional vertices for entry/departure of  
> the
> hex to control for that (where all of the entry vertices are defined as a
> joint set).
>
> Thus I will live with the simple definition for now and leave the more  
> complex
> cases for later.

If you're going to switch to the 2-phased approach, this situation will be  
easy to describe through segment exclusions - two segments terminating in  
different cities on the same hex are mutually exclusive for the same train.