Ex Bibliotheca

The life and times of Zack Weinberg.

Sunday, 29 September 2002

# 6:50 PM

c99 section 6.5 paragraph 7 rears its controversial head again

It happens about once a year. Some programmer discovers that their code has been "mis-optimized" by GCC, files a bug report, and we point out that it doesn't obey the rules in the above-mentioned section of the C standard. Thus GCC is allowed to do whatever it pleases to their code, up to and including replacing it with an invocation to make demons fly out of your nose (when executed, not at compile time). They come back with "but it's obvious what this code is intended to do, you should get it right anyway!" and the thread degenerates into name-calling and references to the Halting Problem.

The 1999 instance of this argument is particularly long, painful, and has Richard Stallman in it; but thankfully I seem to have stayed out of it. Alas, not so this year.

The "demons fly out of your nose" quip is due to John Woods, who also invented a line which I had on a button on my backpack for a long time:

SCSI is NOT magic. There are fundamental technical reasons why you have to sacrifice a young goat to your SCSI chain every now and then.

The button had no attribution. I'd just like to say thank you, John.

# 5:50 AM

Because I'm tired and procrastinating... let's have a tinfoil hat joke, from Warehouse 23:

you open one of the 1008 boxes on this floor and find...

A set of one dozen MIB-grade tinfoil hat-liners with complete instructions on their construction and use to prevent the effects of mind-control rays. They would work, but are now of merely historical interest, as the mind control system has since been upgraded and will bypass protection of this nature.

In the other random thoughts department, a number of new apartment buildings around here have this nifty racked storage system for cars. It's basically two fixed platforms on a hydraulic lift, which can rise or fall to bring either platform to the level of the garage floor. This lets them get twice as many cars into the floorspace. But to do it, they have to dig a pit under the platforms, to give the lift somewhere to go. There's space for another row of cars there, but it can't be used.

How would your friendly local mad scientist fit more cars into this space? Consider the humble fifteen puzzle. Any of the tiles can be brought to the lower right-hand corner. Now imagine that you have a parking garage laid out like this. Instead of tiles, you have motorized platforms with cars on them. To get a car out of this garage, you rearrange the platforms until the one you want is adjacent to the entrance, then drive the car away. To put it back, rearrange the platforms until an empty one is at the entrance, then drive the car on.

There's no reason to restrict this system to two dimensions; the platforms could easily be stacked to fill whatever space is available. It can store as many cars as could theoretically be crammed into the space, less one for the required empty cell. (Assuming of course that all cars are the same size, but this assumption is shared by the original system I described.)