1. Introduction

The Zephyr Abstract Syntax Description Lanuguage (ASDL) is a language designed to describe the tree-like data structures in compilers. Its main goal is to provide a method for compiler components written in different languages to interoperate. ASDL makes it easier for applications written in a variety of programming languages to communicate complex recursive data structures.

asdlGen is a tool that takes ASDL descriptions and produces implementations of those descriptions in a variety of popular languages. ASDL and asdlGen together provide the following advantages

• Concise descriptions of important data structures.
• Automatic generation of data structure implementations for C, C++, Java, Standard ML, and Haskell.
• Automatic generation of functions to read and write the data structures to disk in a machine and language independent way.

ASDL descriptions describe the tree-like data structures such as abstract syntax trees (ASTs) and compiler intermediate representations (IRs). Tools such as asdlGen automatically produce the equivalent data structure definitions for C, C++, Java, Standard ML, and Haskell. asdlGen also produces functions for each language that read and write the data structures to and from a platform and language independent sequence of bytes. The sequence of bytes is called a pickle.

ASDL pickles can be interactively viewed and edited with a graphical browser, or pretty printed into a simple textual format. The browser provides some advanced features such as display styles and tree based versions of standard unix tools such as diff and grep. ASDL is part of the Zephyr National Compiler Infrastructure project.