feat: better recursive descent

pkg/saccharine/stringify.go

@@ -1,36 +1,31 @@
 package saccharine
 
-import "strings"
+import (
+	"strings"
 
-type stringifyVisitor struct {
-	builder strings.Builder
+	"git.maximhutz.com/max/lambda/pkg/saccharine/ast"
+)
+
+type stringifyVisitor struct{}
+
+func (v stringifyVisitor) VisitAtom(n *ast.Atom) string {
+	return n.Name
 }
 
-func (v *stringifyVisitor) VisitVariable(a *Variable) {
-	v.builder.WriteString(a.Name)
+func (v stringifyVisitor) VisitAbstraction(n *ast.Abstraction) string {
+	return "\\" + strings.Join(n.Parameters, " ") + "." + ast.Visit(v, n.Body)
 }
 
-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(n *ast.Application) string {
+	arguments := []string{ast.Visit(v, n.Abstraction)}
 
-func (v *stringifyVisitor) VisitApplication(c *Application) {
-	v.builder.WriteRune('(')
-	c.Abstraction.Accept(v)
-
-	for _, argument := range c.Arguments {
-		v.builder.WriteRune(' ')
-		argument.Accept(v)
+	for _, argument := range n.Arguments {
+		arguments = append(arguments, ast.Visit(v, argument))
 	}
 
-	v.builder.WriteRune(')')
+	return "(" + strings.Join(arguments, " ") + ")"
 }
 
-func Stringify(n Node) string {
-	b := &stringifyVisitor{}
-	n.Accept(b)
-	return b.builder.String()
+func Stringify(n ast.Expression) string {
+	return ast.Visit(&stringifyVisitor{}, n)
 }