feat: add De Bruijn indexed reduction engine #33

2026-01-17T00:36:29Z

mvhutz commented

2026-01-17 00:36:29 +00:00

Context

This PR implements issue #26, adding a De Bruijn indexed reduction engine as an alternative to the standard lambda calculus interpreter.

Summary

Add -i flag to select interpreter (lambda or debruijn)
Create debruijn package with Expression types:
- Variable with integer index and optional label
- Abstraction without named parameter (parameter is implicit)
- Application same as lambda
Implement shift and substitute operations for De Bruijn indices
Add conversion functions between lambda and De Bruijn representations
Update CLI to support switching between interpreters
Add De Bruijn tests to verify all samples pass

Test Plan

All existing lambda interpreter tests pass
All De Bruijn interpreter tests pass with same expected output
Invalid interpreter flag returns appropriate error
Both interpreters produce identical results for all test samples

Closes #26

## Context This PR implements issue #26, adding a De Bruijn indexed reduction engine as an alternative to the standard lambda calculus interpreter. ## Summary - Add `-i` flag to select interpreter (`lambda` or `debruijn`) - Create `debruijn` package with Expression types: - `Variable` with integer index and optional label - `Abstraction` without named parameter (parameter is implicit) - `Application` same as lambda - Implement shift and substitute operations for De Bruijn indices - Add conversion functions between lambda and De Bruijn representations - Update CLI to support switching between interpreters - Add De Bruijn tests to verify all samples pass ## Test Plan - [x] All existing lambda interpreter tests pass - [x] All De Bruijn interpreter tests pass with same expected output - [x] Invalid interpreter flag returns appropriate error - [x] Both interpreters produce identical results for all test samples Closes #26

mvhutz added 1 commit 2026-01-17 00:36:30 +00:00

feat: add De Bruijn indexed reduction engine 528956b033

Add a new interpreter option (-i debruijn) that uses De Bruijn indices
for variable representation, eliminating the need for variable renaming
during substitution.

- Add -i flag to select interpreter (lambda or debruijn)
- Create debruijn package with Expression types (Variable with index,
  Abstraction without parameter, Application)
- Implement shift and substitute operations for De Bruijn indices
- Add conversion functions between lambda and De Bruijn representations
- Update CLI to support switching between interpreters
- Add De Bruijn tests to verify all samples pass

Closes #26

mvhutz added 1 commit 2026-01-17 19:53:10 +00:00

feat: progress 21ae2ca91c

mvhutz closed this pull request

2026-01-17 19:53:15 +00:00

Pull request closed

Please reopen this pull request to perform a merge.

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Reference: mvhutz/lambda#33