feat: new engine format

pkg/emitter/emitter.go

@@ -1,46 +0,0 @@
-package emitter
-
-import "git.maximhutz.com/max/lambda/pkg/set"
-
-type Emitter[E comparable] interface {
-	On(E, func()) Listener[E]
-	Off(Listener[E])
-	Emit(E)
-}
-
-type BaseEmitter[E comparable] struct {
-	listeners map[E]set.Set[Listener[E]]
-}
-
-func (e *BaseEmitter[E]) On(kind E, fn func()) Listener[E] {
-	if e.listeners[kind] == nil {
-		e.listeners[kind] = set.New[Listener[E]]()
-	}
-
-	listener := &BaseListener[E]{kind, fn}
-	e.listeners[kind].Add(listener)
-	return listener
-}
-
-func (e *BaseEmitter[E]) Off(listener Listener[E]) {
-	kind := listener.Kind()
-	if e.listeners[kind] != nil {
-		e.listeners[kind].Remove(listener)
-	}
-}
-
-func (e *BaseEmitter[E]) Emit(event E) {
-	if e.listeners[event] == nil {
-		e.listeners[event] = set.New[Listener[E]]()
-	}
-
-	for listener := range e.listeners[event].Items() {
-		listener.Run()
-	}
-}
-
-func New[E comparable]() *BaseEmitter[E] {
-	return &BaseEmitter[E]{
-		listeners: map[E]set.Set[Listener[E]]{},
-	}
-}

pkg/emitter/listener.go

@@ -1,19 +0,0 @@
-package emitter
-
-type Listener[E comparable] interface {
-	Kind() E
-	Run()
-}
-
-type BaseListener[E comparable] struct {
-	kind E
-	fn   func()
-}
-
-func (l BaseListener[E]) Kind() E {
-	return l.kind
-}
-
-func (l BaseListener[E]) Run() {
-	l.fn()
-}

pkg/engine/engine.go

@@ -1,11 +1,12 @@
+// Package engine defines a general process of reducing a lambda calculus
+// expression.
 package engine
 
-type Engine[T any] interface {
-	Load() Process[T]
-}
-
+// A Process handles the reduction of a
 type Process[T any] interface {
 	Get() (T, error)
-	Set(T) error
 	Step(int) bool
 }
+
+// An Engine is an object that handles
+type Engine[T any] = func(T) (Process[T], error)

pkg/engine/normalorder/engine.go

@@ -1,3 +1,5 @@
+// Package normalorder contains an engine that reduces a 'lambda.Expression'
+// in the normal order.
 package normalorder
 
 import (
@@ -5,20 +7,20 @@ import (
 	"git.maximhutz.com/max/lambda/pkg/lambda"
 )
 
-type Process struct {
+type process struct {
 	expr lambda.Expression
 }
 
-func (e Process) Get() (lambda.Expression, error) {
+func (e process) Get() (lambda.Expression, error) {
 	return e.expr, nil
 }
 
-func (e *Process) Set(l lambda.Expression) error {
+func (e *process) Set(l lambda.Expression) error {
 	e.expr = l
 	return nil
 }
 
-func (e *Process) Step(i int) bool {
+func (e *process) Step(i int) bool {
 	for range i {
 		next, reduced := ReduceOnce(e.expr)
 		if !reduced {
@@ -31,12 +33,10 @@ func (e *Process) Step(i int) bool {
 	return true
 }
 
-type Engine struct {
+// NewProcess creates a new redution process.
+func NewProcess(expression lambda.Expression) (engine.Process[lambda.Expression], error) {
+	return &process{expr: expression}, nil
 }
 
-func (e Engine) Load() engine.Process[lambda.Expression] {
-	return &Process{}
-}
-
-var _ engine.Process[lambda.Expression] = (*Process)(nil)
-var _ engine.Engine[lambda.Expression] = (*Engine)(nil)
+var _ engine.Process[lambda.Expression] = (*process)(nil)
+var _ engine.Engine[lambda.Expression] = NewProcess

pkg/engine/normalorder/reduce_once.go

@@ -2,6 +2,11 @@ package normalorder
 
 import "git.maximhutz.com/max/lambda/pkg/lambda"
 
+// ReduceOnce attempts to apply a single reduction to a lambda expression.
+// It returns (1) the final expression (reduced, or not), and (2) whether or not
+// a reduction was applied.
+//
+// If a reduction is not applied, it returns the original expression.
 func ReduceOnce(e lambda.Expression) (lambda.Expression, bool) {
 	switch e := e.(type) {
 	case lambda.Abstraction: