Multicategorical Semantics for Untyped Effects

Fuente: arXiv
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Main Authors: Grunfeld, Ariel, Cohen, Liron
Format: Preprint
Published: 2026
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_version_ 1866910241301463040
author Grunfeld, Ariel
Cohen, Liron
author_facet Grunfeld, Ariel
Cohen, Liron
contents Completeness proofs in categorical semantics usually proceed by building a syntactic category whose composition is given by substitution. For untyped effectful Call-by-Value languages, this runs into a basic obstacle: there is no canonical notion of simultaneous substitution of computations, since evaluation order is semantically meaningful. We address this by taking single computation substitutions, that is, binding steps, as primitive, and representing computation substitution by finite sequential lists composed by concatenation. We formalize this idea in a one-object Freyd-multicategorical setting. We introduce Freyd operads, separating a cartesian operad of values from a symmetric Ren-cartesian preoperad of computations, connected by a Freyd functor, and from any Freyd operad we construct a corresponding Freyd PROP of substitutions. We prove that this construction is representable and, in the strict one-object setting, left adjoint to restriction to codomain 1. Using the induced term model, we interpret untyped computational lambda-calculus with procedures and higher-order functions in weakly closed Freyd operads, and prove soundness, initiality, and completeness. This yields a categorical semantics tailored to untyped effectful computation and broad enough to encompass realizability-oriented models such as monadic combinatory algebras.
format Preprint
id arxiv_https___arxiv_org_abs_2605_21337
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Multicategorical Semantics for Untyped Effects
Grunfeld, Ariel
Cohen, Liron
Programming Languages
Category Theory
18C50 (Primary) 18C15, 18D15, 18M65, 18M85 (Secondary)
D.3.1; F.3.2; F.4.1
Completeness proofs in categorical semantics usually proceed by building a syntactic category whose composition is given by substitution. For untyped effectful Call-by-Value languages, this runs into a basic obstacle: there is no canonical notion of simultaneous substitution of computations, since evaluation order is semantically meaningful. We address this by taking single computation substitutions, that is, binding steps, as primitive, and representing computation substitution by finite sequential lists composed by concatenation. We formalize this idea in a one-object Freyd-multicategorical setting. We introduce Freyd operads, separating a cartesian operad of values from a symmetric Ren-cartesian preoperad of computations, connected by a Freyd functor, and from any Freyd operad we construct a corresponding Freyd PROP of substitutions. We prove that this construction is representable and, in the strict one-object setting, left adjoint to restriction to codomain 1. Using the induced term model, we interpret untyped computational lambda-calculus with procedures and higher-order functions in weakly closed Freyd operads, and prove soundness, initiality, and completeness. This yields a categorical semantics tailored to untyped effectful computation and broad enough to encompass realizability-oriented models such as monadic combinatory algebras.
title Multicategorical Semantics for Untyped Effects
topic Programming Languages
Category Theory
18C50 (Primary) 18C15, 18D15, 18M65, 18M85 (Secondary)
D.3.1; F.3.2; F.4.1
url https://arxiv.org/abs/2605.21337