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>
12 lines
484 B
Go
12 lines
484 B
Go
// Package expr provides the abstract Expression interface for all evaluatable
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// expression types in the lambda interpreter.
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package expr
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// Expression is the base interface for all evaluatable expression types.
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// Different evaluation modes (lambda calculus, SKI combinators, typed lambda
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// calculus, etc.) implement this interface with their own concrete types.
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type Expression interface {
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// String returns a human-readable representation of the expression.
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String() string
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}
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