feat: better recursive descent

pkg/saccharine/ast/node.go

@@ -0,0 +1,41 @@
+package ast
+
+type Expression interface {
+	IsExpression()
+}
+
+/** ------------------------------------------------------------------------- */
+
+type Abstraction struct {
+	Parameters []string
+	Body       Expression
+}
+
+type Application struct {
+	Abstraction Expression
+	Arguments   []Expression
+}
+
+type Atom struct {
+	Name string
+}
+
+/** ------------------------------------------------------------------------- */
+
+func NewAbstraction(parameter []string, body Expression) *Abstraction {
+	return &Abstraction{Parameters: parameter, Body: body}
+}
+
+func NewApplication(abstraction Expression, arguments []Expression) *Application {
+	return &Application{Abstraction: abstraction, Arguments: arguments}
+}
+
+func NewAtom(name string) *Atom {
+	return &Atom{Name: name}
+}
+
+/** ------------------------------------------------------------------------- */
+
+func (a Abstraction) IsExpression() {}
+func (a Application) IsExpression() {}
+func (v Atom) IsExpression()        {}