Models of a Non-associative Composition

We characterise the polarised evaluation order through a categorical structure where the hypothesis that composition is associative is relaxed. Duploid is the name of the structure, as a reference to Jean-Louis Loday’s duplicial algebras. The main result is a reflection Adj → Dupl where Dupl is a category of duploids and duploid functors, andAdj is the category of adjunctions and pseudo maps of adjunctions. The result suggests that the various biases in denotational semantics: indirect, call-by-value, call-by-name... are ways of hiding the fact that composition is not always associative.