feat: stuff

cmd/lambda/lambda.go

@@ -7,7 +7,6 @@ import (
 
 	"git.maximhutz.com/max/lambda/internal/cli"
 	"git.maximhutz.com/max/lambda/internal/config"
-	"git.maximhutz.com/max/lambda/pkg/lambda"
 	"git.maximhutz.com/max/lambda/pkg/saccharine"
 )
 
@@ -31,24 +30,24 @@ func main() {
 	// Turn tokens into syntax tree.
 	expression, err := saccharine.GetTree(tokens)
 	cli.HandleError(err)
-	logger.Info("Parsed syntax tree.", "tree", lambda.Stringify(expression))
+	logger.Info("Parsed syntax tree.", "tree", saccharine.Stringify(expression))
 
 	// Reduce expression.
 	start := time.Now()
 
 	if options.Explanation {
-		fmt.Println(lambda.Stringify(expression))
+		fmt.Println(saccharine.Stringify(expression))
 	}
 
-	for lambda.ReduceOnce(&expression) {
-		logger.Info("Reduction.", "tree", lambda.Stringify(expression))
-		if options.Explanation {
-			fmt.Println("    =", lambda.Stringify(expression))
-		}
-	}
+	// for lambda.ReduceOnce(&expression) {
+	// 	logger.Info("Reduction.", "tree", saccharine.Stringify(expression))
+	// 	if options.Explanation {
+	// 		fmt.Println("    =", saccharine.Stringify(expression))
+	// 	}
+	// }
 
 	elapsed := time.Since(start).Milliseconds()
 
-	fmt.Println(lambda.Stringify(expression))
+	fmt.Println(saccharine.Stringify(expression))
 	fmt.Fprintln(os.Stderr, "Time Spent:", elapsed, "ms")
 }

pkg/saccharine/ast.go

@@ -1,7 +1,7 @@
 package saccharine
 
 type Node interface {
-	IsNode()
+	Accept(Visitor)
 }
 
 /** ------------------------------------------------------------------------- */
@@ -36,6 +36,14 @@ func NewVariable(name string) *Variable {
 
 /** ------------------------------------------------------------------------- */
 
-func (_ Abstraction) IsNode() {}
-func (_ Application) IsNode() {}
-func (_ Variable) IsNode()    {}
+func (a *Abstraction) Accept(x Visitor) { x.VisitAbstraction(a) }
+func (a *Application) Accept(x Visitor) { x.VisitApplication(a) }
+func (v *Variable) Accept(x Visitor)    { x.VisitVariable(v) }
+
+/** ------------------------------------------------------------------------- */
+
+type Visitor interface {
+	VisitAbstraction(*Abstraction)
+	VisitApplication(*Application)
+	VisitVariable(*Variable)
+}

pkg/saccharine/stringify.go

@@ -0,0 +1,36 @@
+package saccharine
+
+import "strings"
+
+type stringifyVisitor struct {
+	builder strings.Builder
+}
+
+func (v *stringifyVisitor) VisitVariable(a *Variable) {
+	v.builder.WriteString(a.Name)
+}
+
+func (v *stringifyVisitor) VisitAbstraction(f *Abstraction) {
+	v.builder.WriteRune('\\')
+	v.builder.WriteString(strings.Join(f.Parameters, " "))
+	v.builder.WriteRune('.')
+	f.Body.Accept(v)
+}
+
+func (v *stringifyVisitor) VisitApplication(c *Application) {
+	v.builder.WriteRune('(')
+	c.Abstraction.Accept(v)
+
+	for _, argument := range c.Arguments {
+		v.builder.WriteRune(' ')
+		argument.Accept(v)
+	}
+
+	v.builder.WriteRune(')')
+}
+
+func Stringify(n Node) string {
+	b := &stringifyVisitor{}
+	n.Accept(b)
+	return b.builder.String()
+}

samples/saccharine.txt

@@ -1,5 +1,5 @@
 0 := \f x.x
-inc n := \f x.(f (n f x))
+inc n := \f x.f (n f x)
 add n m := m inc n
 mult n m := m (n f)
 exp m n := m n

samples/simple.txt

@@ -12,5 +12,5 @@
     )
     \n f x.(f (n f x))
   )
-  \f x.x
+  \f x.((((((x))))))
 )