In a previous post I introduced the libpq PostgreSQL C library and used it to create a database, a few tables and a view. In this post I will demonstrate inserting, updating, deleting and selecting data using the database created in the previous post.
Every time I need to work with dates and times in C I find myself scrabbling around trying to refresh my memory on how the data structures and functions provided by time.h work. I have therefore put together a short program to demo the most important functionality, mainly as a reference for myself but I hope you find it useful as well.
This article is the first in a series covering the use of the PostgreSQL RDBMS with C using the official libpq library. In this post I will introduce the library with a simple program which creates a database and then adds a few tables and views. In future articles I’ll cover DML or CRUD: inserting, querying, updating, deleting data, and also reading database schemas.
For this post I will write a simple implementation of a 1-dimensional cellular automaton in C. The concept of cellular automata has existed since the middle of the 20th century and has grown into a vast field with many practical and theoretical applications.
A cellular automaton consists of any number of "cells" arranged in 1, 2, 3s or more dimensions. Each has a state associated with it (in the simplest case just on or off) and each cell and therefore the entire automaton transitions from one state to the next over time according to a rule or set of rules.
The number of dimensions, the number of possible cell states, and the rules can become arbitrarily large and complex but for this project I will implement the simplest type of one-dimensional cellular automaton, known as an elementary cellular automaton.
I recently wrote a post on Pascal's Triangle and in this post I will write a program in C to implement a Galton Board simulator, a Galton Board being an actual physical gadget following the Pascal Triangle's probabilistic characteristics.
A while ago I wrote an implementation of the Soundex Algorithm which attempts to assign the same encoding to words which are pronounced the same but spelled differently. In this post I'll cover the Levenshtein Word Distance algorithm which is a related concept measuring the "cost" of transforming one word into another by totalling the number of letters which need to be inserted, deleted or substituted.
The Levenshtein Word Distance has a fairly obvious use in helping spell checkers decided which words to suggest as alternatives to mis-spelled words: if the distance is low between a mis-spelled word and an actual word then it is likely that word is what the user intended to type. However, it can be used in any situation where strings of characters need to be compared, such as DNA matching.
I started off calling this project "Calculating Pi" but soon realised that I needed to rename it "Estimating Pi". Pi is an irrational number starting off 3.14159 and then carrying on for an infinite number of digits with no pattern which anybody has ever discovered. Therefore it cannot be calculated as such, just estimated to (in principle) any number of digits.
The C99 standard introduced the _Bool type as well as stdbool.h which allows you to use bool, true and false. _Bool uses a byte to store true/false, yes/no, on/off or whatever the semantics of your program might be, but of course you only really need 1 bit so 7 bits are wasted. Most of the time this isn't worth worrying about but in some rare cases where you need a lot of Booleans it might be worthwhile looking into ways of being a bit more efficient with memory usage. This article presents my particular approach to doing this.
This post will demonstrate programs which each perform a single very specific task but which can be chained together in such a way that the output of one forms the input of another. Connecting programs like this, or piping to use the correct terminology, enables more complex workflows or processes to be run.
This post includes just three short programs to carry out the following tasks: