Hacker News: BobMackay

New comment by BobMackay in "Wavy walls use fewer bricks than a straight wall (2020)"

BobMackay — Thu, 27 Jul 2023 15:36:25 +0000

I think one should also consider the failure modes when, for example, a tree falls into the wall. For a straight wall, it is possible that a falling section will propagate the failure along the entire length of the wall. For a wavy wall, it is likely to fail in shear, limiting the damage to one section.

New comment by BobMackay in "Unicode Character “𝕏” (U+1D54F)"

BobMackay — Mon, 24 Jul 2023 15:06:33 +0000

I understand equations, both the simple and quadratical!

New comment by BobMackay in "An Aperiodic Monotile Exists!"

BobMackay — Thu, 23 Mar 2023 04:16:50 +0000

I have been waiting for this for 50 years! It is wonderful that Roger Penrose and my father, Alan Mackay, are still alive to see it! If only Escher could see it!

New comment by BobMackay in "Kathleen Booth, the inventor of assembly language, has died"

BobMackay — Sat, 29 Oct 2022 19:46:01 +0000

Thanks. My copy was actually the copy that they sent to J.D. Bernal, and was signed over to him "with the compliments of the authors". My father was another PhD student of Bernal's, and became Professor of Crystallography at Birkbeck later. The diagrams are scanned in from the original, but I re-typed the text for web presentation. It is astonishing how much of Computer Science was completely understood by the end of the war.

New comment by BobMackay in "Kathleen Booth, the inventor of assembly language, has died"

BobMackay — Sat, 29 Oct 2022 15:36:57 +0000

Here is their 1947 paper on Principles and Progress in the Construction of High-Speed Digital Computers: http://bobmackay.com/Booth/Booth.html

New comment by BobMackay in "Switcher (2004)"

BobMackay — Fri, 12 Aug 2022 03:07:51 +0000

I was present at the BMUG meeting on Berkeley campus when Andy demonstrated Switcher for the first time. He did no talking, but simply ran up two or three applications... and then the whole screen scrolled sideways and the audience was on its feet cheering! The event was amazing, only perhaps matched by Bill Atkinson's demo of Hypercard. Happy days!

New comment by BobMackay in "507 Mechanical Movements (1868)"

BobMackay — Sun, 07 Mar 2021 17:05:47 +0000

If you like such things, Nguyen Duc Thang has a ridiculously extensive collection he has been modeling, which can be seen at https://www.youtube.com/user/thang010146/featured.

New comment by BobMackay in "The first use of the term “programming language”?"

BobMackay — Thu, 26 Dec 2019 05:03:05 +0000

The notion of "Programming" was mentioned and even defined in 1947 by Donald Booth. See http://bobmackay.com/Booth/Booth.html Principles and Progress in the Construction of High-Speed Digital Computers.

"The word 'programme' as used in this context may require explanation. Before a problem is ready for solution in a computing machine it must first be broken up into processes which the machine is capable of performing. Thus, as mentioned above, when using a digital machine the continuous process of differentiation must be replaced by a finite difference formula. This translating of a problem in terms of the available functions of the machine is generally known as programming."

However he did not use the word "language" as only assembler was known at the time, and he was the first to use even that.

New comment by BobMackay in "Impossible Cookware and Other Triumphs of the Penrose Tile"

BobMackay — Sat, 09 Feb 2019 17:23:43 +0000

I don't have a 3d printer - Shapeways is much more convenient and cheaper!

New comment by BobMackay in "Impossible Cookware and Other Triumphs of the Penrose Tile"

BobMackay — Sat, 09 Feb 2019 17:23:04 +0000

It is a BlueChick, from BuildYourCNC.

I recommend it if all you wish to cut is wood. It is not really stiff enough for aluminum. A great starter machine. Mine is starting to wear out the rails, so I am in the course of building a new one based on 8020 tubing, which is going to have a much larger carvable envelope.

New comment by BobMackay in "Impossible Cookware and Other Triumphs of the Penrose Tile"

BobMackay — Sat, 09 Feb 2019 02:03:51 +0000

My father (Professor Alan Mackay) and I visited Professor Penrose in Oxford in 1975, to discuss his new tiling pattern, and I was able to write a computer program (in Algol 60) to draw it on a graph plotter. See http://bobmackay.com/Penrose/PenroseColour300.jpg

My father generated a diffraction pattern from this, using light rather than X-rays, and so was able to predict the pattern eventually discovered by Dan Shechtman some years later.

You might also be amused by a weave based on the pattern, with threads going in five different directions: http://bobmackay.com/PentaTable/index.html

I would be in the market for some of this cookware, but I suspect that it is apocryphal.

New comment by BobMackay in "The geometry of Islamic art becomes a game"

BobMackay — Thu, 26 Oct 2017 16:10:13 +0000

Just as a heads up, if you try to run this program with your monitor in portrait mode, the program defaults to full screen mode, but assumes a landscape monitor. The parts that are cut off are critical to getting the program to do anything at all, since you have to start by clicking on a green window that is off the side of the screen. Nice music though...

New comment by BobMackay in "“Eeny, meeny, miny, mo” and the ambiguous history of counting-out rhymes (2015)"

BobMackay — Thu, 01 Jun 2017 15:48:03 +0000

This counting-out game is known as the Josephus Problem, and dates back many centuries. See https://en.wikipedia.org/wiki/Josephus_problem. I have a wood-block printed Japanese textbook from around 1700 with a good account of the problem.

New comment by BobMackay in "The Patek Philippe Caliber 89 and Horology’s Easter Problem"

BobMackay — Sat, 06 May 2017 03:11:22 +0000

Just for completeness, the 1990 paper referred to was by my father, Professor Alan Mackay, and was published in Modern Physics Letters B, Vol 4, No 15. I have put up a roughly scanned copy at http://bobmackay.com/Alan/AlanCV120.pdf in case anyone is interested.