Wednesday, November 21, 2007

Simplicity is in the eye of the beholder

Laurent has posted a particularly succinct method for doing bitwise aggregations on his blog. I don't know what practical use it is, but that's another matter. What I liked was his cheeky sign-off, "It is that easy!". Which reminded me of a story from years ago, when I was still in the Ministry of Defence

I was sent on a CORAL 66 course. CORAL was a 3GL intended for real-time programming and it combined keywords in English with some very low level functionality, including the ability to flip individual bits. As a COBOL bunny with a History degree this was this first time I'd ever had to wrangle bitmasks and it made my brain hurt. I wasn't lucky enough to be sent on the subsequent advanced course (five weeks long, those were the days!) but these who did got to build either a missile guidance system or a safety system for a nuclear power station in their exercises. Even on the beginners' course the exercises were fairly hard going.

One involved translating Morse code into letters. I went for a data-intensive solution. I wrote an array with all the letters in the Morse alphabet. This was hard work but the actual processing was quite simple: start in the middle of the array and shift the index left or right depending upon whether the current character is a dot or a dash, halving the offset each time. When there's no further input the index points to the transmitted letter.

There was a very bright chap on the course. We often talk about junior programmers, but this guy was definitely junior, because he was a lance corporal and so everybody else on the course outranked him. Even me: as a civvy I had a notional rank of lieutenant. Most of the trainers were officers but there was a sergeant whose job it was to answer the questions of the non-comm students (they weren't allowed to ask officers questions or indeed initiate any conversation).

Anyway, this corporal's solution consist of a single very dense recursive algorithm which somehow spat out the right answer. However, his code contained just the one comment: "This algorithm is easy to understand so no further explanation is necessary." The trainers didn't understand his algorithm and he knew they wouldn't understand it and they knew that was why he had put the comment in. So they marked him down, for insubordination.



Blogger Laurent Schneider said...

for insubordination
Lol ! it reminds me programming a battleship game in pascal at high school, I used internal register to capture mouse movements, and used temp files for network intercommunication, when I was supposed to do something like for i in 1 to 10 print 10. I had very few spaces and carriage returns, forget about new lines or comments... guess my teacher had the same feeling/reaction as your trainer 8-)

21 November 2007 at 10:53:00 GMT-8  
Blogger Niall said...

ah I had an annoying, and hugely intelligent, maths teacher at school (Q hi there!) who tended at the 'leap of imagination' moments in mathematical proofs to write

clearly ...

whereas in fact the line was anything but clear. He also did it to provoke - but in a teacher that's pretty good.

21 November 2007 at 14:36:00 GMT-8  

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