Dependently Typed Attribute Grammars

Abstract

Attribute Grammars (AGs) are a domain-specific language for functional and composable descriptions of tree traversals. Given such a description, it is not immediately clear how to state and prove properties of AGs formally. To meet this challenge, we apply dependent types to AGs. In a dependently typed AG, the type of an attribute may refer to values of attributes. The type of an attribute is an invariant, the value of an attribute a proof for that invariant. Additionally, when an AG is cycle-free, the composition of the attributes is logically consistent. We present a lightweight approach using a preprocessor in combination with the dependently typed language Agda.