feat: stuff

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()
+}