I have a related question to this, if you’re storing [“hello”] as one chunk, what happens when you perform an edit to say adding an extra [“e”] after the [“e”]? In the unoptimised structure I know you can just add the new [“e”] as a child of the original [“e”]. So here would you then delete the chunk [“hello”] and split it into two halves like [“he”] and [“llo”]?
Yes exactly. You replace the chunk with “he” and “llo” then insert the extra item in the middle. The result is [“he”, “e”, “llo”]. The code to do all this inline in a b-tree is pretty hairy but it works pretty well!
Honest question - do you find generated code to be useful? I've always had a very strong bias against it, due to the fact that implementation details can vary so widely.
Hi everyone, I am an indie iOS/Mac developer (4 years!), I made this Mac app originally to help myself keep track of all my projects. The aim is to keep tasks organised as well as files and emails (you can link messages from Mail.app as well as gmail links). I know there are various web based solutions, but I travel a lot so don’t always have a good connection.
Also noise and ride comfort. In Warsaw we have some really old Soviet subway cars and a mix of western/homegrown ones
While the bumpy ride is just a nuissance, the noise of those old junkers probably should require everyone to wear heavy hearing protection, if one had to adhere to workplace regulation.
When their crooked boogies start to screech and grind in turns, the noise is physically painful
> Old carriages might not meet modern expectations of crashworthiness or fire resistance.
Since we're talking about Berlin, the new airport had a similar problem: Because of all the delays and problems, the construction permit expired. And it could not just be reissued for the same plans because safety and energy conservation regulations had become tighter in the meantime. As far as I know, parliament extended the construction permit manually to avoid the replanning costs.
Melbourne did this a few years back; they bought back (for a princely sum) some carriages sold for a pittance a few years earlier to cover a shortage in rolling stock.
> I mean surely the actual carriage of the train can be reused, but with just the engine refitted.
Vivarail (http://www.vivarail.co.uk/) are doing almost exactly this in the UK with late-70s London Underground trains, fitting modern electronics and Ford truck engines as generators for the electric motors. I think it's a solid idea.
Have Vivarail managed to find any customers yet? From an engineering point of view what they knocked together looked quite good, but for the UK market right now it's just a disaster. You can't spend billions upgrading London trains, and then suggest knocking together some franken-pacer out of London's scraps to replace the terrible units in the north and west-country.
Typically you'd also have to refit the train control system that communicates with the trackside equipment and the odometry system. On older trains you might run into problems because the brakes don't prevent locking and mess up the odometry so you'd have to refit those as well.
Nevertheless, there are plenty of really old trains still running. Service times of fourty years and more are the rule, not the exception.
> Service times of fourty years and more are the rule, not the exception.
Is this different between trains and trams? In Dresden, our rolling stock of trams is between 10 and 20 years old (with half a dozen older trains reserved to cover high load situations), and the tram operator is already loudly thinking about ordering the next generation.
Lighter vehicles tend to have less durable construction. When it comes to low floor trams/railcars, the lack of space is another engineering problem. Plus, with a high-floor vehicle, you have lots of space during rebuilds to install newer power electronics and auxiliary equipment, in order to extend the service life. Regular heavy-rail, high floor metro EMUs can go for over half a century.
I wonder if these trains have air conditioning. Berlin might not need it, but if you had a subway train without air conditioning in NYC for example, the passengers would boil. So that might explain it.
