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CodePlea
Random thoughts on programming
30 Nov 2016

Interpolating in a Triangle


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

V1V2V3

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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11 Feb 2016

Succinct Code


I like simple things. It should be self-evident - I recently ditched WordPress for a hundred lines of PHP and flat-files. I'm much happier for it.

I used to write a lot of C++ code, but for the last several years I've completely eschewed it in favor of C. I can't ever see myself ever going back to C++, as I feel like C is a better language, and it's much easier to keep a large project nice and neat using it. C++ code has a tendency to grew crufty almost from the start. C++ has more abstractions, and although all abstracts are leaky, I think C++ lends itself to creating especially leaky abstractions. C++ makes it much easier to build yourself into a corner compared to C.

Anyway, a few days ago I witnessed an exchange on Stack Overflow that I thought was interesting. It pretty well illustrated some of the differences I find between C and C++ code. And also showcased some of the problems I have with Stack Overflow in general.

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01 Feb 2016

Ditching Wordpress


This site has been running WordPress since the beginning.

Today I moved it to my own CMS (which I will open-source one of these days). I've integrated comments using Disqus.

WordPress isn't bad per se, but it tries to do everything. That makes it extremely complex. I like simple things. Now I feel like I can really tweak the site's functionality. I think I'll be much happier going forward with my flat-file CMS.

Hopefully nothing was broken in the transfer. I think all the URLs have stayed the same and all the old comments transferred over.

21 Jan 2016

Math Expression Parsing in C


I published some code over at Github today. It's a tiny library called TinyExpr. It parses, compiles, and evaluates math expressions.

    #include "tinyexpr.h"
    #include <stdio.h>

    int main(int argc, char *argv[])
    {
        const char *expression = "sqrt(5^2+7^2+11^2+(8-2)^2)";
        printf("Result: %f\n", te_interp(expression, 0));
        return 0;
    }

Anyway, it's quite fast, and it has other features like variable binding. It's all implemented in one ANSI C source file with no dependencies. Check it out!

05 Nov 2015

Uploading to GitHub


I've decided to publish some of my side projects over at GitHub. Right now it's just PlusCallback (C++ callback library) and Minctest (a tiny ANSI C unit-testing framework). Hopefully this will help me keep a bit more organized, and help me publish some more code.

I'm currently working on several side projects I'd like to open source in the next several months:

  • A tiny PHP CMS
  • A simple artificial neural network library in C
  • A financial technical analysis project
  • A numerical optimization library in C

For older articles, please see the archive.