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This article is part of Series On Regular Expressions.  For more examples of regular expressions to visualize, check out this this list of Regular Expression Test Cases. Your Regex: String To Search: Generate New Random Matching String The Regex As A C Program Common C Code For All Regular Expressions The C source code below is the common code that is required by any of the code samples that are g

2019-08-01 - By Robert Elder This article will discuss the setup steps that are required for recording videos at high frame rates on cheap Raspberry Pi cameras.  Frame rates up to 660FPS on the V1 camera and up to 1007 on the V2 camera can be achieved.  Filming at these extremely high frame rates on a Raspberry Pi is much more challenging and involves more work than typical point and shoot photogr

2017-06-07 - By Robert Elder Below you will find example source code and interactive visualizations that are intended to complement the paper 'An O(ND) Difference Algorithm and Its Variations' by Eugene W. Myers[1].  Multiple variants of the algorithms discussed in Myers' paper are presented in this article, along with working source code versions of the pseudo-code presented in the paper. Two ref

2016-07-07 - By Robert Elder Updated July 15, 2016: Emphasize that declarators and declarations are completely different things. Updated July 8, 2016: Corrections related to spiral rule and K & R C style declarators.  See comment on HN discussion Introduction This will be the first part in a series of posts that are intended to document my thoughts during the process of building a type system for

2016-04-05 - By Robert Elder Updated April 10, 2016: Removed use of unnecessary brackets as per suggestion Updated April 7, 2016: Use 'cit' instead of 'vitx', correction about identity functions vs idempotence. On Hacker News Introduction In this article, a method for inserting vim into the middle of a unix pipe is presented.  This method has several caveats, but it can produce extremely terse and

2016-03-04 - By Robert Elder Last Updated Dec 12, 2019:  Fixed an off by one error (awk uses 1-based arrays!). The Command cat /dev/urandom | hexdump -v -e '/1 "%u\n"' | awk '{ split("0,2,4,5,7,9,11,12",a,","); for (i = 0; i < 1; i+= 0.0001) printf("%08X\n", 100*sin(1382*exp((a[$1%8+1]/12)*log(2))*i)) }' | xxd -r -p | aplay -c 2 -f S32_LE -r 16000 The above command was tested on Ubuntu 14.04.  You

2016-02-01 - By Robert Elder Last Updated:  Sept 29, 2016 Synopsis An interface can be thought of as a contract between the system and the environment.  In a computer program, the 'system' is the function or module in question, and the 'environment' is the rest of the project.  The interface formally describes what can pass between the system and the environment.  An 'implementation' can be define

2016-01-10 - By Robert Elder Introduction I just finished updating my C compiler and minimal CPU specification to include virtual memory.  The process of adding virtual memory support to a CPU, a kernel, and a compiler toolchain has made me realize that there is a lack of good explanations for how all of these parts fit together.  I also realized that a surprising number of programming decisions e

2015-05-25 - By Robert Elder In my attempts to learn the C programming language well enough to write my own C compiler, I've encountered some very interesting examples of C syntax that you generally don't see every day.  All of these examples you'll see here will compile without warnings or errors even with very strict compiler flags in gcc and clang (gcc -Wall -ansi -pedantic -std=c89 main.c).  H

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