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[VA] Short & Sweet Math Challenges #23: "May the 4th Be With You !" Special
05-17-2018, 09:12 PM
Post: #22
RE: [VA] Short & Sweet Math Challenges #23: "May the 4th Be With You !" ...
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Hi, Jeff O, Maximilian Hohmann and brickviking:

Jeff O Wrote:Upon further review, Step the 6th is the kind of number manipulation challenge that I have enjoyed attempting on various models [...] With that said, reading that Egan put 3 hours and one sleepless night into it, and it will continue to haunt him, kind of scares me off a bit.

No need to be afraid, Egan was probably trying to scare would-be solvers, actually it's not that difficult. On hindsight, I probably goofed badly when I put this lovely problem last after a row of essentially 71B-only, tricky ones, so people failed to notice its generality (more or less solvable in every machine) and classic nature. My bad.

Quote:My usual inclination with such problems is to just go ahead and try for a brute force method, then try to optimize. The DM42 is fast, I would like to see how many digits it could handle in a reasonable time by brute force, so if I get the time I may have a go at it.

Please do. I haven't created a solution for the DM42 but I guesstimate that with correct programming it can solve the 11-digit version in 5 min. to 1 hour running time.

Quote:In any case, thanks for your challenges, please don’t be put off by a lower than hoped-for response. Next time I’ll be sure to read through more carefully!

Thank you very much, you'll be welcome to try. I feel better now. :-D

Maximilian Hohmann Wrote:Although I [...] would not have been able to solve a single one of these challenges. Especially the ones which require PEEKing the digits of mathematical constants out of the ROM... (The last time I wrote the word "PEEK" before this reply must have been ca. 1983 when I did some machine language programming on my Sinclair ZX81).

He he, same here ! I also had a Sinclair ZX81 back then and also did Z80A machine language programming, most especially video games and graphics routines. I got many books dealing with the matter (which I still keep to this day), most of them truly excellent, and learned a lot. I remember writing my Bombardier game utterly by hand, with no compilers or any other tools, painstakingly computing the offsets for the jumps by sheer byte-counting, etc., and being ecstatic when it run fine the first time I tried it, not even a single bug or miscalculation. Those were the days ... !

Quote:Nonetheless these challenges and the answers are a pleasure to read and think about!

Thank you very much for your kind words, much appreciated. See below for something on PEEK ... :-)

brickviking Wrote:PEEK and POKE have interesting results on a SHARP PC-1247. I got several somewhat unexpected results by poking instruction codes directly into program memory, as that was within the range of program listings.

It's quite similar to the way we HP calc fans initially discovered synthetics in the HP-41C. We would enter data in storage registers and thanks to Bug 2 it would appear in program memory as various synthetic functions, most notably STO M, N, and such. My first HP-41C was a very early model with all the bugs. Regrettably, I eventually sold it and the next HP-41C I got didn't have Bug 2 anymore.

Quote:As the 1247 only had 3328 bytes of addressable memory, it wasn't considered "big iron" enough for what I thought I wanted out of a programmable calculator. It certainly wasn't in the same league as the 71B or 75C/D (but was probably considerably cheaper).

Much cheaper. And the 71B was also much cheaper (and 5 times slower !) than the 75CD (which I never liked, too bulky, bad keyboard layout, mediocre BASIC).

Best regards to all.
V.
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RE: [VA] Short & Sweet Math Challenges #23: "May the 4th Be With You !" ... - Valentin Albillo - 05-17-2018 09:12 PM



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