Modeling Tactics as Operators: Effect-Grounded Representations for Lean Theorem Proving

Elisaveta Samoylov, Soroush Vosoughi


Abstract
Interactive theorem provers (ITPs) such as Lean expose proof construction as a sequence of tactics applied to proof states. Existing machine learning approaches typically treat tactics either as surface tokens or as labels conditioned on the current state, eliding their operator-like semantics. This paper introduces a representation learning framework in which tactics are characterized by the changes they induce on proof states. Using a stepwise Lean proof corpus, we construct delta contexts—token-level additions/removals and typed structural edits—and train simple distributional models (𝛥-SGNS and CBOW-𝛥) to learn tactic embeddings grounded in these state transitions. Experiments on tactic retrieval and operator-style analogy tests show that 𝛥-supervision yields more interpretable and generalizable embeddings than surface-only baselines. Our findings suggest that capturing the semantics of tactics requires modeling their state-transformational effects, rather than relying on distributional co-occurrence alone.
Anthology ID:
2025.mathnlp-main.12
Volume:
Proceedings of The 3rd Workshop on Mathematical Natural Language Processing (MathNLP 2025)
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Marco Valentino, Deborah Ferreira, Mokanarangan Thayaparan, Leonardo Ranaldi, Andre Freitas
Venues:
MathNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
168–175
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URL:
https://preview.aclanthology.org/ingest-emnlp/2025.mathnlp-main.12/
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Cite (ACL):
Elisaveta Samoylov and Soroush Vosoughi. 2025. Modeling Tactics as Operators: Effect-Grounded Representations for Lean Theorem Proving. In Proceedings of The 3rd Workshop on Mathematical Natural Language Processing (MathNLP 2025), pages 168–175, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
Modeling Tactics as Operators: Effect-Grounded Representations for Lean Theorem Proving (Samoylov & Vosoughi, MathNLP 2025)
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https://preview.aclanthology.org/ingest-emnlp/2025.mathnlp-main.12.pdf