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arXiv · 2510.16133

Typing Strictness (Extended Version)

Daniel Sainati·Joseph W. Cutler·Benjamin C. Pierce·Stephanie Weirich
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Abstract

Strictness analysis is critical to efficient implementation of languages with non-strict evaluation, mitigating much of the performance overhead of laziness. However, reasoning about strictness at the source level can be challenging and unintuitive. We propose a new definition of strictness that refines the traditional one by describing variable usage more precisely. We lay type-theoretic foundations for this definition in both call-by-name and call-by-push-value settings, drawing inspiration from the literature on type systems tracking effects and coeffects. We prove via a logical relation that the strictness attributes computed by our type systems accurately describe the use of variables at runtime, and we offer a strictness-annotation-preserving translation from the call-by-name system to the call-by-push-value one. All our results are mechanized in Rocq.

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Daniel Sainati, Joseph W. Cutler, Benjamin C. Pierce, Stephanie Weirich. 2025-10-17. Typing Strictness (Extended Version). https://arxiv.org/abs/2510.16133

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