Blog Archives

Where combinator names come from

Today I found out where the one-letter names of some functions in combinatory logic come from. I’d seen these before (for example, in To Mock a Mockingbird) but I had no idea what inspired the names. These functions — I,

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Core memory

Here’s something I saw framed on a client’s wall today. The plaque reads IBM 360 MODEL 25 CORE MEMORY CIRCA 1968 2K BYTES Here’s a close-up that shows the cores, little ring magnets at the intersection of wires. Related post:

Posted in Computing

Most popular tech notes for 2013

Here are some of the technical notes that have been popular on my site this year. R for programmers coming from other languages C++ regular expressions Probability distribution chart PowerShell Cookbook Computing running variance (and higher moments) Floating point exceptions

Posted in Computing

Comparing Windows and Linux stability

In my experience, Ubuntu 12.04 is less stable than Windows 8. Ubuntu is more likely to freeze, crash, or otherwise act badly than Windows. When I say this, people point out that Ubuntu is not the Linux kernel and that

Posted in Computing

Calculating entropy

For a set of positive probabilities pi summing to 1, their entropy is defined as (For this post, log will mean log base 2, not natural log.) This post looks at a couple questions about computing entropy. First, are there

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Posted in Computing, Math

Leading digits and quadmath

My previous post looked at a problem that requires repeatedly finding the first digit of kn where k is a single digit but n may be on the order of millions or billions. The most direct approach would be to

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Posted in Computing

Baroque computers

From an interview with Neal Stephenson, giving some background for his Baroque Cycle: Leibniz [1646-1716] actually thought about symbolic logic and why it was powerful and how it could be put to use. He went from that to building a

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Appreciation for plain text

My attitude toward plain text files:

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Preparing for Google Reader going away

As you’ve probably heard, Google has announced that they’re discontinuing Google Reader on July 1. Most of you who subscribe to this blog use Google Reader or use an RSS reader that depends on Google’s Feedfetcher. Here’s a snapshot from

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Wonky but free

Rachel Kroll wrote a blog post last Friday entitled I mortgaged my future with a Mac. The part I found most interesting is near the end of the post. Instead of staying with my wonky-but-free ways of doing things, I

Posted in Computing

Seven John McCarthy papers in seven weeks

I recently ran across a series of articles from Carin Meier going through seven papers by the late computer science pioneer John McCarthy in seven weeks. Published so far: Prologue #1: Ascribing Mental Qualities to Machines #2: Towards a Mathematical

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No technology can ever be too arcane

In this fake interview, Linux creator Linus Torvalds says Linux has gotten too easy to use and that’s why people use Git: Git has taken over where Linux left off separating the geeks into know-nothings and know-it-alls. I didn’t really

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Posted in Computing, Software development

It's not the text editor, it's text

Vivek Haldar had a nice rant about editors a couple days ago. In response to complaints that some editors are ugly, he writes: The primary factor in looking good should be the choice of a good font at a comfortable

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Posted in Computing

Second-generation public-key cryptography

This review of a book on elliptic curves summarizes what has happened with public-key cryptography. In a nutshell, methods like RSA were the first generation, and elliptic curve methods are the second generation. Second-generation methods provide more security per bit.

Posted in Computing

Why computers were invented

From a lecture by Gregory Chaitin: We all know that the computer is a very practical thing out there in the real world … But what people don’t remember as much is that really — I’m going to exaggerate, but

Posted in Computing, Math