https://github.com/andreasabel/constraint-based-type-inference

Agda formalization of constraint-based type inference for the simply-typed lambda-calculus
https://github.com/andreasabel/constraint-based-type-inference

Last synced: 3 months ago
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Agda formalization of constraint-based type inference for the simply-typed lambda-calculus

• Host: GitHub
• URL: https://github.com/andreasabel/constraint-based-type-inference
• Owner: andreasabel
• License: bsd-3-clause
• Created: 2024-02-06T20:10:07.000Z (over 2 years ago)
• Default Branch: master
• Last Pushed: 2024-02-06T20:37:00.000Z (over 2 years ago)
• Last Synced: 2025-10-10T19:20:38.202Z (9 months ago)
• Language: Agda
• Size: 6.84 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# constraint-based-type-inference

An Agda formalization of constraint-based type inference for the simply-typed lambda-calculus.

Uses a de Bruijn representation of type variables.

The implementation of the occurs-check follows:

> Conor McBride, First-Order Unification by Structural Recursion, Journal of Functional Programming, 2003.

Type inference is split into a first pass extracting constraints between types,

and a second pass solving the constraints by first-order unification.

Constraint-based type inference has been systematically described by:

> Francois Pottier and Didier Rémy, The Essence of ML Type Inference.

> In B. C. Pierce, Advanced Topics in Types and Programming Languages, The MIT Press, 2004.

So do not expect any new ideas here.  Just enjoy the Agda code!

Limitations (as of 2024-02-06):

- Just specification (judgements), no algorithm (functions).

- Only soundness, no completeness.

- No `let`-generalization / ML-polymorphism.

Tested with:

- Agda 2.6.4.1 and agda-stdlib 2.0

Related work:

- https://github.com/wenkokke/FirstOrderUnificationInAgda