Bidirectional parsing a functional/logic perspective

We introduce PURE, a pure declarative approach to implementing declarative transformations with declarative tools. This DomainSpecific Language (DSL), inspired by the Definite Clause Grammar (DCG) and Parsing Expression Grammar (PEG) formalisms, is implemented using the Revised Report on the Algorithmic Language Scheme (R5RS). Thanks to its use of the MINIKANREN logic programming system it supports fully reversible and extensible syntax-semantics relations. In this paper we highlight the usability and simplicity of PURE’s approach, address the problem of leftrecursion and show how its features help in defining custom and extensible typing systems for JavaScript Object Notation (JSON).