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We give a new proof of the well-known fact that all functions $(\mathbb{N} \to \mathbb{N}) \to \mathbb{N}$ which are definable in G\"odel's System T are continuous via a syntactic approach. Differing from the usual syntactic method, we…

Logic · Mathematics 2023-06-22 Chuangjie Xu

Standard Transformers excel at semantic modeling but struggle with rigid sequential logic and state tracking. Theoretical work establishes that self-attention is limited to $\AC^0$ (under hard attention) or $\TC^0$ (under soft attention),…

Machine Learning · Computer Science 2026-02-10 Mehryar Mohri

We investigate families of infinite automata for context-sensitive languages. An infinite automaton is an infinite labeled graph with two sets of initial and final vertices. Its language is the set of all words labelling a path from an…

Logic in Computer Science · Computer Science 2017-01-11 Arnaud Carayol , Antoine Meyer

In this paper, we investigate the problem of synthesizing computable functions of infinite words over an infinite alphabet (data $\omega$-words). The notion of computability is defined through Turing machines with infinite inputs which can…

Formal Languages and Automata Theory · Computer Science 2023-06-22 Léo Exibard , Emmanuel Filiot , Nathan Lhote , Pierre-Alain Reynier

We show that equivalence of deterministic top-down tree-to-string transducers is decidable, thus solving a long standing open problem in formal language theory. We also present efficient algorithms for subclasses: polynomial time for total…

Formal Languages and Automata Theory · Computer Science 2017-01-30 Helmut Seidl , Sebastian Maneth , Gregor Kemper

We consider finite state non-deterministic but unambiguous transducers with infinite inputs and infinite outputs, and we consider the property of Borel normality of sequences of symbols. When these transducers are strongly connected, and…

Formal Languages and Automata Theory · Computer Science 2020-06-17 Olivier Carton

A language over an alphabet $B = A \cup \overline{A}$ of opening ($A$) and closing ($\overline{A}$) brackets, is balanced if it is a subset of the Dyck language $D_B$ over $B$, and it is well-formed if all words are prefixes of words in…

Formal Languages and Automata Theory · Computer Science 2020-03-16 Raphaela Löbel , Michael Luttenberger , Helmut Seidl

This paper introduces a robust class of functions from finite words to integers that we call Z-polyregular functions. We show that it admits natural characterizations in terms of logics, Z-rational expressions, Z-rational series and…

Formal Languages and Automata Theory · Computer Science 2023-04-19 Thomas Colcombet , Gaëtan Douéneau-Tabot , Aliaume Lopez

Transformers are arguably the preferred architecture for language generation. In this paper, inspired by continued fractions, we introduce a new function class for generative modeling. The architecture family implementing this function…

Computation and Language · Computer Science 2026-05-25 Amit Dhurandhar , Vijil Chenthamarakshan , Dennis Wei , Tejaswini Pedapati , Karthikeyan Natesan Ramamurthy , Rahul Nair

A fundamental question in interpretability research is to what extent neural networks, particularly language models, implement reusable functions through subnetworks that can be composed to perform more complex tasks. Recent advances in…

Machine Learning · Computer Science 2025-06-24 Philipp Mondorf , Sondre Wold , Barbara Plank

We answer an open question in the theory of transducer degrees initially posed in [1] on the existence of a diamond structure in the transducer hierarchy. Transducer degrees are the equivalence classes formed by word transformations which…

Formal Languages and Automata Theory · Computer Science 2023-01-18 Noah Kaufmann

We prove a characterization of first-order string-to-string transduction via $\lambda$-terms typed in non-commutative affine logic that compute with Church encoding, extending the analogous known characterization of star-free languages. We…

Logic in Computer Science · Computer Science 2024-12-18 Cécilia Pradic , Ian Price

Permutation rational functions over finite fields have attracted high interest in recent years. However, only a few of them have been exhibited. This article studies a class of permutation rational functions constructed using trace maps on…

Number Theory · Mathematics 2024-01-01 Ruikai Chen , Sihem Mesnager

We answer an open question in the theory of transducer degrees on the existence of a diamond structure in the transducer hierarchy. Transducer degrees are the equivalence classes formed by word transformations which can be realized by a…

Formal Languages and Automata Theory · Computer Science 2025-12-17 Noah Kaufmann

Nobody knows how language works, but many theories abound. Transformers are a class of neural networks that process language automatically with more success than alternatives, both those based on neural computations and those that rely on…

Computation and Language · Computer Science 2024-08-08 Felix Hill

The notion of delay between finite transducers is a core element of numerous fundamental results of transducer theory. The goal of this work is to provide a similar notion for more complex abstract machines: we introduce a new notion of…

Formal Languages and Automata Theory · Computer Science 2024-04-30 Emmanuel Filiot , Ismaël Jecker , Christof Löding , Sarah Winter

Language is typically modelled with discrete sequences. However, the most successful approaches to language modelling, namely neural networks, are continuous and smooth function approximators. In this work, we show that Transformer-based…

Computation and Language · Computer Science 2025-04-08 Samuele Marro , Davide Evangelista , X. Angelo Huang , Emanuele La Malfa , Michele Lombardi , Michael Wooldridge

Consider a continuous word embedding model. Usually, the cosines between word vectors are used as a measure of similarity of words. These cosines do not change under orthogonal transformations of the embedding space. We demonstrate that,…

Computation and Language · Computer Science 2019-05-28 Alexey Zobnin

In this report, we consider extended real-valued functions on some real vector space. Gerstewitz functionals are used to construct all translative functions. We derive formulas for translative functions which are lower semicontinuous,…

Optimization and Control · Mathematics 2018-11-02 Petra Weidner

Deterministic two-way transducers on finite words have been shown by Engelfriet and Hoogeboom to have the same expressive power as MSO-transductions. We introduce a notion of aperiodicity for these transducers and we show that aperiodic…

Formal Languages and Automata Theory · Computer Science 2021-03-30 Olivier Carton , Luc Dartois