Stream processors and comodels

06/10/2021

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by   Richard Garner, et al.

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In 2009, Ghani, Hancock and Pattinson gave a coalgebraic characterisation of stream processors A^ℕ→ B^ℕ drawing on ideas of Brouwerian constructivism. Their stream processors have an intensional character; in this paper, we give a corresponding coalgebraic characterisation of extensional stream processors, i.e., the set of continuous functions A^ℕ→ B^ℕ. Our account sites both our result and that of op. cit. within the apparatus of comodels for algebraic effects originating with Power-Shkaravska.