INC: A Language for Incremental Computations

Abstract

An incremental computation is one that is performed repeatedly on nearly identical inputs. Incremental computations occur naturally in many environments, such as compilers, language-based editors, spreadsheets, and formatters. This article describes a proposed tool for making it easy to write incremental programs. The tool consists of a programming language, INC, and a set of compile-time transformations for the primitive elements of INC. A programmer defines an algorithm in INC without regard to efficient incremental execution. The transformations automatically convert this algorithm into an efficient incremental algorithm. INC is a functional language. The implementation of an INC program is a network of processes. Each INC function is transformed into a process that receives and transmits messages describing changes to its inputs and outputs. We give an overview to the language and illustrate the incremental techniques employed by INC. We present the static and incremental complexity bounds for the primitive INC functions. We also present some example programs illustrating INC's flexibility. © 1991, ACM. All rights reserved.