Zip Files All The Way Down
research.swtch.com
research.swtch.com
(Zeros are as good as ones and converting doesn't cost high-quality energy. It's deleting information. Thus going from an unknown state to a defined state cost high-quality energy, i.e. has to increase entropy elsewhere.)
:; gunzip -l tb1.gz ; gunzip tb1.gz; mv tb1 tb1.gz
compressed uncompressed ratio uncompressed_name
43863 55982 21.7% tb1
:; gunzip -l tb1.gz ; gunzip tb1.gz; mv tb1 tb1.gz
compressed uncompressed ratio uncompressed_name
55982 2568864 97.8% tb1
:; gunzip -l tb1.gz ; gunzip tb1.gz; mv tb1 tb1.gz
compressed uncompressed ratio uncompressed_name
2568864 1067044016 99.8% tb1
:; gunzip -l tb1.gz ; gunzip tb1.gz; mv tb1 tb1.gz
compressed uncompressed ratio uncompressed_name
1067044016 0 0.0% tb1
What's your sample size?
I spent several years in a company that developed this sort of products and I am not aware of any commercial products that do what you described. I am guessing you are referring to the mail gateways integrated with FOSS virus scanners, and still I doubt the behavior you described is typical even between them. From what I saw the restrictions were implemented in the scanners themselves, and the mail that could not be readily processed was always quarantined, and not simply "not delivered".
And I was trying to play a nice little trick on a few of my friends with that one, too...
So we'd forward the phone that way, then call it from another line. You'd hear a sequence of clicks, progressively quieter (why? isn't it all digital?), and then it would just stop, presumably because all external lines were used up.
Farther off topic, the phone system had a weird feature: dialing #*5 would say back to you 3 (apparently) random digits. This was good for chemistry lab, if you needed to fudge some data and wanted to introduce a believable error factor into it.
Since analog connections lose power with distance, there was defined an acceptable maximum loss for each segment in the network. If a line came in too hot, a "pad" was added to dissipate some power at the receiving end. If it was too low, the circuit was out of spec and had to be re-engineered.
At the other end of the telephone switch, an amplifier was added to jack up all the outgoing signals to the proper amplitude for the transmission network.
All this amplification and loss was necessary to make sure that all telephone calls had about the same volume. The network didn't all switch over to digital switching and transmission in one day (in fact there are some analog interoffice circuits still in use to this day in Alaska), so we retained some vestiges of the loss plan.
It's pretty likely that your PBX system connected to the network over analog lines anyway. :)
[ [ dup curry ] dup curry ]
When called, it puts [ dup curry ] on the stack, then creates a copy of it on the stack. curry then takes the second block from the stack and prepends it to the first. Rather than being a program that evaluates to its code, it's a code block that evaluates to itself (similar to most Scheme/Lisp quines).
(Off topic note: I originally read the title of the article as "Zip Flies All The Way Down" and was wondering what zipping my fly down had to do with hacker news.)
And isn't it rather the fixed point of the unzip function? (Is `zip' even a function (i.e. is `unzip' injective?))