CMPH - C Minimal Perfect Hashing Library. C Algorithms. Quaternions. This page is an introduction to Quaternions, the pages below this have more detail about their algebra and how to use them to represent 3D rotations.
Introduction Quaternions were discovered on 16 October 1843 by William Rowan Hamilton. He spent years trying to find a three dimensional number systems, but with no success, when he looked in 4 dimensions instead of 3 it worked. Quaternions form an interesting algebra where each object contains 4 scalar variables (sometimes known as Euler Parameters not to be confused with Euler angles), these objects can be added and multiplied as a single unit in a similar way to the usual algebra of numbers. However, there is a difference, unlike the algebra of scalar numbers qa * qb is not necessarily equal to qb * qa (where qa and qb are quaternions). Sphlib 3.0. Overview Sphlib is a set of implementations of various hash functions, both in C and in Java.
The C code is meant to be easily imported into other projects, in particular embedded systems. The Java code implements an API somewhat similar to that of java.security.MessageDigest. The C source code also provides two standalone tools: