pyPEG is a quick and easy solution for creating a parser in Python programs. pyPEG uses a PEG language in Python data structures to parse, so it can be used dynamically to parse nearly every context free language. The output is a plain Python data structure called pyAST, or, as an alternative, XML.
EFEU is suitable for handling data cubes, which are especially useful for building data warehouses. It consists of a building system including mkmf (a xmkmf like Makefile generator), esh (a powerful C/C++ interpreter), efeudoc (a document generator with different output formats (LaTeX, HTML, roff, etc.)). EFEU has a huge set of C library core features, including robust memory allocation tools, functions to concatenate and copy strings with memory allocation, buffers for dynamically-growing strings and fields, data structures with reference counters and garbage collection, and file tools that allow you to specify pipes wherever a filename is expected and support automatic implementation of (de)compression filters (gzip) depending on filename extensions. It also includes a high-level interface to files, strings, and anything else you can read from or write to.
VFGEN is a program that takes a specification of a vector field (in other words, a system of differential equations) and generates source code for a wide variety of ODE solvers and other numerical tools. It includes a command for generating C code to be used with the CVODE solver.
Yacas is a general purpose, easy to use Computer Algebra System (a CAS is a program that can be used to do symbolic manipulation of mathematical expressions). It is built on top of its own programming language designed for this purpose, in which new algorithms can easily be implemented. In addition, it comes with extensive documentation on the functionality implemented and methods used to implement them.