M.V. Hutz
e0114c736d
## Description The codebase currently couples the engine and plugins directly to `lambda.Expression`. This PR introduces an abstract `expr.Expression` interface to enable future support for multiple evaluation modes. - Add `pkg/expr/expr.go` with an `Expression` interface requiring a `String()` method. - Update `lambda.Expression` to embed `expr.Expression`. - Add `String()` method to `Abstraction`, `Application`, and `Variable` types. - Update plugins to use `String()` instead of `lambda.Stringify()`. ### Decisions - The `expr.Expression` interface is minimal (only `String()`) to avoid over-constraining future expression types. - The engine still stores `*lambda.Expression` directly rather than `expr.Expression`, because Go's interface semantics require pointer indirection for in-place mutation during reduction. - Future evaluation modes will implement their own concrete types satisfying `expr.Expression`. ## Benefits - Establishes a foundation for supporting multiple evaluation modes (SKI combinators, typed lambda calculus, etc.). - Plugins now use the abstract `String()` method, making them more decoupled from the lambda-specific implementation. - Prepares the codebase for a Reducer interface abstraction in a future PR. ## Checklist - [x] Code follows conventional commit format. - [x] Branch follows naming convention (`<type>/<description>`). - [x] Tests pass (if applicable). - [ ] Documentation updated (if applicable). Reviewed-on: #30 Co-authored-by: M.V. Hutz <git@maximhutz.me> Co-committed-by: M.V. Hutz <git@maximhutz.me>
24 lines
416 B
Go
24 lines
416 B
Go
package plugins
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import (
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"log/slog"
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"git.maximhutz.com/max/lambda/internal/engine"
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)
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type Logs struct {
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logger *slog.Logger
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process *engine.Engine
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}
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func NewLogs(logger *slog.Logger, process *engine.Engine) *Logs {
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plugin := &Logs{logger, process}
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process.On(engine.StepEvent, plugin.Step)
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return plugin
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}
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func (t *Logs) Step() {
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t.logger.Info("reduction", "tree", (*t.process.Expression).String())
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}
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