A simple economy engine. The engine is an implementation of the methods discussed in the following article: http://larc.unt.edu/techreports/LARC-2010-03.pdf
The price resolution technique is discussed here in the following article. Additionally, price belief updates could be carried out using a modified Roth-Erev algorithm, also discussed in the article as applied to a discriminatory double-auction. http://www2.econ.iastate.edu/tesfatsi/mpeieee.pdf
The price & speculator models are discussed in http://www.cs.princeton.edu/~ken/scott.pdf