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Random thoughts on programming
20 Feb 2017

Get an email whenever you're mentioned online

I've published a few open source projects, and I noticed that sometimes they would be posted on social media sites such as Hacker News, Reddit, Lobsters, etc. Sometimes I wouldn't notice these posts until days later (if ever), which meant that I did not have an opportunity to join in the discussion.

So I built a bot that scrapes these sites and scans for keywords. It sends me an email whenever one of my projects is mentioned. I decided that it would be pretty easy to turn it into a free service that others might enjoy, and so I did.

It's called F5Bot. F5Bot just takes a list of keywords and will send you an email whenever one of those keywords is mentioned on the social media sites it monitors. It's totally free, so signup and give it a try!

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06 Jan 2017

Incomplete Beta Function in C

The Incomplete Beta function, or regularized incomplete beta function, seems to be one of those functions that should be built into the standard libraries, but is conspicuously missing. It shows up all over the place in statistics. It's crucial to Student's t distribution, which is likely the second most important distribution in statistics after the Gaussian distribution.

a chart showing the incomplete beta function for different values of a and b

I couldn't find an open-source implementation to fit my exact needs, so I'm going to give simple C code to compute it.

If you're just looking for code, check out the Github repo. If you want to learn how it works, keep reading.

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22 Dec 2016

GoAccess, Analytics, and PHP

GoAccess is an excellent open source web log analyzer. It makes nice, fancy charts and such:

Screenshot of GoAccess output

GoAccess has several modes of running, including outputting HTML, or severing HTML live with its built-in webserver. I knew I wanted to use GoAccess to analyze my server logs, but I wasn't sure what the best way to use it was.

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19 Dec 2016

Technical Analysis Library

I recently released a technical analysis library called Tulip Indicators under the LGPL license. If you need to do technical analysis, I think it's the best library out there now.

I also released a companion project called Tulip Cell which provides the functions to Excel spreadsheets via an add-in.

And finally, I'm working on a full featured charting program that I plan to release soon: Tulip Charts.

30 Nov 2016

Interpolating in a Triangle

Let's say we have a triangle. Maybe something like this:


Furthermore, let's say that each vertex (corner) has an associated value of some sort. For example: assume each vertex has an associated color. Perhaps we have:

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23 Aug 2016

Exponentiation Associativity and Standard Math Notation

Someone recently told me that TinyExpr (my math expression evaluation library) had several bugs, mostly related to the precedence and associativity of the exponentiation operator. It turned out that they thought that math notation was more standardized than it actually is.

I made TinyExpr to be used in a spreadsheet-like program. Therefore, I tried to make it somewhat compatible with spreadsheets. This makes for behavior that may surprise some people. For example, TinyExpr evaluates multiple exponentiation from left-to-right by default. This behaviour is clearly documented in the Readme and can be changed with a compile-time flag.

I thought it'd be nice to do a survey of common computer languages and tools and see how they handle exponentiation precedence and associativity.

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18 Mar 2016

Genann - Neural Network Library

I've made a simple neural network library in ANSI C called Genann. I released it as open-source on github recently. You can find it here.

A primary design goal of Genann was to be both complete and minimal. I'm happy with how close I've come to that goal. Genann implements the feed-forward algorithm, backpropagation, and not much else. It's not opinionated about how you store your data or about how you do training. It is contained in just a single C source file and header file.

Genann is also very easy to use. For example, creating a network with 2 inputs, 3 hidden neurons, and 2 outputs is as easy as:

/* inputs, hidden layers, neurons per hidden layer, outputs. */
genann *ann = genann_init(2, 1, 3, 2);

Example neural network connection structure.

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23 Feb 2016

Apple and the FBI

The FBI has gotten a court order demanding that Apple help unlock a San Bernardino shooter's work phone, an iPhone 5C.

This has been in the news everywhere for days, and I'm already sick of it, so I'm going to keep this short.

Almost everyone has read Apple's public response, but nobody I've talked to has read the actual court order itself. You're doing yourself a disservice if you don't read the actual court order for yourself. It's three pages, and it's much more precise than Apple's response or anything you'll read in the news.

From the order, we see that the government is asking Apple to do three things:

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For older articles, please see the archive.