[Rails-devel] Train management

[Erik V. <eri...@xs...>]

As announced before, I have been thinking about how to upgrade train
management to enable some new features that currently can't be implemented
(notably items 2 and 5 of the below list).

I'm aware of the following cases to  be taken into account:
1. Normal trains.
2. Dual trains, as in 18VA, 18Scan and 1846 (these are the three games I'm
aware of having such flip-side trains, and which have considered so far).
3. Initial trains (as in 18EU).
4. Fixed trains (at a cost, as some 1825 minors have).
5. Extra trains from a private special property (as in 18GA).
Any others?

The basic idea is to separate train certificates from actual trains.  

Train certificates are objects that can be traded.  Each certificate
represents a potential train, designated by a train type object.  A dual
train certificate represents one of two potential trains, and is therefore
linked to two train type objects.

Trains are objects owned and held by companies only.  Trains are no longer
created at the game start, but at the time that a company acquires a train
by whatever means.  The possibilities are:
1. Buy a normal train certificate: create a train object.
2. Buy a dual train certificate: ask the player what type is wanted (this
can affect the price), and instantiate a train of that train type only.
3. An initial train as in 18EU is obtained by autobuying a train
(certificate) at zero cost at floating time (similar to as it works now).
4. A fixed train as in 1825 is obtained by autobuying a non-tradable train
(perhaps without a certificate) at nonzero cost at floating time.
5. The 18GA extra 2-train is not tradable and is not related to a train
certificate. It is created when a company buys the OSRR private before phase
4.

When a train is traded between companies, both the train certificate and the
train object are moved.
When a train is discarded to the Pool, the train certificate is moved, but
the train object is destroyed.  
These two procedures are formulated this way to precisely implement the very
explicit 18VA dual train rules: when a dual train certificate is traded
between companies, the initial train choice must still be honoured, but when
a train certificate enters the pool, that choice is erased.  As far as I can
see, the 1846 rules are somewhat less explicit but no different. The 18Scan
rules seem to be silent on this matter, but I assume the 18VA rules also
apply to 18Scan. If anyone is aware of different cases, please let me know. 

Any comments?  Do other cases exist that I have overlooked but need be
considered separately?  

Erik.