M.V. Hutz
9c7fb8ceba
## Description The codebase previously used "interpreter" terminology and standalone functions for expression operations. This PR modernizes the architecture by renaming to "runtime" and converting operations to receiver methods. - Rename `pkg/interpreter` to `pkg/runtime`. - Move `ReduceOnce` to new `pkg/normalorder` package for reduction strategy isolation. - Convert standalone functions (`Substitute`, `Rename`, `GetFree`, `IsFree`) to receiver methods on concrete expression types. - Change `Set` from pointer receivers to value receivers for simpler usage. - Update all references from "interpreter" to "runtime" terminology throughout the codebase. ### Decisions - Operations like `Substitute`, `Rename`, `GetFree`, and `IsFree` are now methods on the `Expression` interface, implemented by each concrete type (`Variable`, `Abstraction`, `Application`). - The `normalorder` package isolates the normal-order reduction strategy, allowing future reduction strategies to be added in separate packages. - `Set` uses value receivers since Go maps are reference types and don't require pointer semantics. ## Benefits - Cleaner API: `expr.Substitute(target, replacement)` instead of `Substitute(expr, target, replacement)`. - Better separation of concerns: reduction strategies are isolated from expression types. - Consistent terminology: "runtime" better reflects the execution model. - Simpler `Set` usage without needing to manage pointers. ## Checklist - [x] Code follows conventional commit format. - [x] Branch follows naming convention (`<type>/<description>`). Always use underscores. - [x] Tests pass (if applicable). - [x] Documentation updated (if applicable). Reviewed-on: #39 Co-authored-by: M.V. Hutz <git@maximhutz.me> Co-committed-by: M.V. Hutz <git@maximhutz.me>
36 lines
855 B
Go
36 lines
855 B
Go
package lambda
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func (e Variable) Substitute(target string, replacement Expression) Expression {
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if e.Name() == target {
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return replacement
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}
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return e
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}
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func (e Abstraction) Substitute(target string, replacement Expression) Expression {
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if e.Parameter() == target {
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return e
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}
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body := e.Body()
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param := e.Parameter()
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if replacement.IsFree(param) {
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freeVars := replacement.GetFree()
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freeVars.Merge(body.GetFree())
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freshVar := GenerateFreshName(freeVars)
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body = body.Rename(param, freshVar)
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param = freshVar
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}
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newBody := body.Substitute(target, replacement)
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return NewAbstraction(param, newBody)
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}
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func (e Application) Substitute(target string, replacement Expression) Expression {
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abs := e.Abstraction().Substitute(target, replacement)
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arg := e.Argument().Substitute(target, replacement)
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return NewApplication(abs, arg)
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}
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