abstract = "We have begun exploring code evolution by artificial
economies. We implemented a reinforcement learning
machine called Hayek2 consisting of agents, written in
a machine language inspired by Ray's Tierra, that
interact economically. The economic structure of Hayek2
addresses credit assignment at both the agent and meta
levels. Hayek2 succeeds in evolving code to solve
Blocks World problems, and has been more effective at
this than our hillclimbing program and our genetic
program. Our hillclimber and our GP also performed
well, learning algorithms as strong as a simple search
program that incorporates hand-coded domain knowledge.
We made efforts to optimize our hillclimbing program
and it has features that may be of independent
interest. Our genetic program using crossover performed
far better than a version using other macro-mutations
or our hillclimber, bearing on a controversy in the
Genetic Programming literature.",