refactor: extract Reducer interface and update engine to use abstractions #31

2026-01-16T23:40:31Z

mvhutz commented

2026-01-16 23:40:31 +00:00

Description

This PR builds on #30 to complete the abstraction layer for multi-mode evaluation support.
The engine now accepts abstract expr.Expression and reducer.Reducer types instead of concrete lambda types.

Add pkg/reducer/reducer.go with Reducer interface defining Reduce(expr.Expression, onStep) expr.Expression.
Add pkg/lambda/reducer.go with NormalOrderReducer that wraps the existing ReduceAll logic.
Update engine.Engine to store expr.Expression and reducer.Reducer instead of *lambda.Expression.
Update plugins to use expr.Expression.String() directly (no pointer dereference needed).
Update main and tests to instantiate NormalOrderReducer and pass it to the engine.

Decisions

The Reducer.Reduce method returns the final expression and calls onStep after each reduction step with the current state.
NormalOrderReducer type-asserts to lambda.Expression internally; other expression types are returned unchanged.
The engine updates its Expression field both during reduction (via onStep) and after completion.

Benefits

The engine is now fully decoupled from lambda-specific types.
New evaluation modes can be added by implementing expr.Expression and reducer.Reducer.
Plugins work with any expression type that implements expr.Expression.
Prepares the codebase for SKI combinators, typed lambda calculus, or other future modes.

Checklist

Code follows conventional commit format.
Branch follows naming convention (<type>/<description>).
Tests pass (if applicable).
Documentation updated (if applicable).

Closes #30

## Description This PR builds on #30 to complete the abstraction layer for multi-mode evaluation support. The engine now accepts abstract `expr.Expression` and `reducer.Reducer` types instead of concrete lambda types. - Add `pkg/reducer/reducer.go` with `Reducer` interface defining `Reduce(expr.Expression, onStep) expr.Expression`. - Add `pkg/lambda/reducer.go` with `NormalOrderReducer` that wraps the existing `ReduceAll` logic. - Update `engine.Engine` to store `expr.Expression` and `reducer.Reducer` instead of `*lambda.Expression`. - Update plugins to use `expr.Expression.String()` directly (no pointer dereference needed). - Update main and tests to instantiate `NormalOrderReducer` and pass it to the engine. ### Decisions - The `Reducer.Reduce` method returns the final expression and calls `onStep` after each reduction step with the current state. - `NormalOrderReducer` type-asserts to `lambda.Expression` internally; other expression types are returned unchanged. - The engine updates its `Expression` field both during reduction (via `onStep`) and after completion. ## Benefits - The engine is now fully decoupled from lambda-specific types. - New evaluation modes can be added by implementing `expr.Expression` and `reducer.Reducer`. - Plugins work with any expression type that implements `expr.Expression`. - Prepares the codebase for SKI combinators, typed lambda calculus, or other future modes. ## Checklist - [x] Code follows conventional commit format. - [x] Branch follows naming convention (`<type>/<description>`). - [x] Tests pass (if applicable). - [ ] Documentation updated (if applicable). Closes #30

mvhutz added 1 commit 2026-01-16 23:40:31 +00:00

refactor: extract Reducer interface and update engine to use abstractions a61809ad1d

Introduce reducer.Reducer interface and update the engine to use abstract
expr.Expression and reducer.Reducer types, enabling pluggable reduction
strategies.

- Add pkg/reducer/reducer.go with Reducer interface.
- Add pkg/lambda/reducer.go with NormalOrderReducer implementation.
- Update engine to accept expr.Expression and reducer.Reducer.
- Update plugins to use expr.Expression directly (no pointer dereference).
- Update main and tests to pass reducer to engine.

Closes #30

mvhutz merged commit f8e1223463 into main

2026-01-16 23:42:08 +00:00

mvhutz deleted branch refactor/reducer-interface

2026-01-16 23:42:08 +00:00

mvhutz referenced this issue from a commit

2026-01-16 23:42:09 +00:00

refactor: extract Reducer interface and update engine to use abstractions (#31)

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Reference: mvhutz/lambda#31