  This article describes haggies, a program for the generation of optimised
programs for the efficient numerical evaluation of mathematical expressions. It
uses a multivariate Horner-scheme and Common Subexpression Elimination to
reduce the overall number of operations. The package can serve as a back-end
for virtually any general purpose computer algebra program. Built-in type
inference that allows to deal with non-standard data types in strongly typed
languages and a very flexible, pattern-based output specification ensure that
haggies can produce code for a large variety of programming languages. We
currently use haggies as part of an automated package for the calculation of
one-loop scattering amplitudes in quantum field theories. The examples in this
articles, however, demonstrate that its use is not restricted to the field of
high energy physics.
