On Free Completely Iterative Algebras

Author Jiří Adámek

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Jiří Adámek
  • Czech Technical University Prague, Czech Republic

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Jiří Adámek. On Free Completely Iterative Algebras. In 28th EACSL Annual Conference on Computer Science Logic (CSL 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 152, pp. 7:1-7:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


For every finitary set functor F we demonstrate that free algebras carry a canonical partial order. In case F is bicontinuous, we prove that the cpo obtained as the conservative completion of the free algebra is the free completely iterative algebra. Moreover, the algebra structure of the latter is the unique continuous extension of the algebra structure of the free algebra. For general finitary functors the free algebra and the free completely iterative algebra are proved to be posets sharing the same conservative completion. And for every recursive equation in the free completely iterative algebra the solution is obtained as the join of an ω-chain of approximate solutions in the free algebra.

Subject Classification

ACM Subject Classification
  • Theory of computation → Categorical semantics
  • free algebra
  • completely iterative algebra
  • terminal coalgebra
  • initial algebra
  • finitary functor


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