  In computational cognitive science, the cognitive architecture ACT-R is very
popular. It describes a model of cognition that is amenable to computer
implementation, paving the way for computational psychology. Its underlying
psychological theory has been investigated in many psychological experiments,
but ACT-R lacks a formal definition of its underlying concepts from a
mathematical-computational point of view. Although the canonical implementation
of ACT-R is now modularized, this production rule system is still hard to adapt
and extend in central components like the conflict resolution mechanism (which
decides which of the applicable rules to apply next).
  In this work, we present a concise implementation of ACT-R based on
Constraint Handling Rules which has been derived from a formalization in prior
work. To show the adaptability of our approach, we implement several different
conflict resolution mechanisms discussed in the ACT-R literature. This results
in the first implementation of one such mechanism. For the other mechanisms, we
empirically evaluate if our implementation matches the results of reference
implementations of ACT-R.
