Translation of Tree-Processing Programs into Stream-Processing Programs Based on Ordered Linear Type

Koichi Kodama, Kohei Suenaga, Naoki Kobayashi

Abstract: There are two ways to write a program for manipulating tree-structured data such as XML documents and S-expressions: One is to write a tree-processing program focusing on the logical structure of the data and the other is to write a stream-processing program focusing on the physical structure. While tree-processing programs are easier to write than stream-processing programs, tree-processing programs are less efficient in memory usage since they use trees as intermediate data. Our aim is to establish a method for automatically translating a tree-processing program to a stream-processing one in order to take the best of both worlds. We define a programming language for processing binary trees and a type system based on ordered linear type, and show that every well-typed program can be translated to an equivalent stream-processing program.