feat: repr, codec

pkg/repr/repr.go

@@ -0,0 +1,15 @@
+// Package repr defines a general definition of a representation of lambda
+// calculus.
+package repr
+
+import "fmt"
+
+// Repr is a representation of lambda calculus.
+type Repr interface {
+	fmt.Stringer
+
+	// Id returns to name of the objects underlying representation. If is
+	// assumed that if two Repr objects have the same Id(), they share the same
+	// representation.
+	Id() string
+}