style: moved isViable to reducer

pkg/lambda/reduce.go

@@ -1,30 +0,0 @@
-package lambda
-
-func IsViable(e *Expression) (*Abstraction, Expression, bool) {
-	if e == nil {
-		return nil, nil, false
-	} else if app, appOk := (*e).(*Application); !appOk {
-		return nil, nil, false
-	} else if fn, fnOk := app.abstraction.(*Abstraction); !fnOk {
-		return nil, nil, false
-	} else {
-		return fn, app.argument, true
-	}
-}
-
-func ReduceAll(e *Expression, step func()) {
-	it := NewIterator(e)
-
-	for !it.Done() {
-		if fn, arg, ok := IsViable(it.Current()); !ok {
-			it.Next()
-		} else {
-			it.Swap(Substitute(fn.body, fn.parameter, arg))
-			step()
-
-			if _, _, ok := IsViable(it.Parent()); ok {
-				it.Back()
-			}
-		}
-	}
-}

pkg/lambda/reducer.go

@@ -26,6 +26,18 @@ func (r *NormalOrderReducer) Expression() expr.Expression {
 	return r.expression
 }
 
+func isViable(e *Expression) (*Abstraction, Expression, bool) {
+	if e == nil {
+		return nil, nil, false
+	} else if app, appOk := (*e).(*Application); !appOk {
+		return nil, nil, false
+	} else if fn, fnOk := app.abstraction.(*Abstraction); !fnOk {
+		return nil, nil, false
+	} else {
+		return fn, app.argument, true
+	}
+}
+
 // Reduce performs normal order reduction on a lambda expression.
 // The expression must be a lambda.Expression; other types are returned unchanged.
 func (r *NormalOrderReducer) Reduce() {
@@ -33,13 +45,13 @@ func (r *NormalOrderReducer) Reduce() {
 	it := NewIterator(&r.expression)
 
 	for !it.Done() {
-		if fn, arg, ok := IsViable(it.Current()); !ok {
+		if fn, arg, ok := isViable(it.Current()); !ok {
 			it.Next()
 		} else {
 			it.Swap(Substitute(fn.body, fn.parameter, arg))
 			r.Emit(reducer.StepEvent)
 
-			if _, _, ok := IsViable(it.Parent()); ok {
+			if _, _, ok := isViable(it.Parent()); ok {
 				it.Back()
 			}
 		}