There is a close connection between machine learning and compression: a system that predicts the posterior probabilities of a sequence given its entire history can be used for <answer>optimal</answer> data compression (by using arithmetic coding on the output distribution) while an <answer>optimal</answer> compressor can be used for prediction (by finding the symbol that compresses best, given the previous history). This equivalence has been used as a justification for using data compression as a benchmark for "general intelligence."
What type of compressor can be used for prediction?
optimal