The Synthesizer Generator

Programs are hierarchical compositions of formulae satis-fying structural and extra-structural relationships. A pro-gram editor can use knowledge of such relationships to detect and provide immediate feedback about violations of them. The Synthesizer Generator is a tool for creating such editors from language descriptions. An editor designer specifies the desired relationships and the feed-back to be given when they are violated, as well as a user interface; from the specification, the Synthesizer Generator creates a full-screen editor for manipulating programs in the language. 1. In t roduct ion With the Cornell Program Synthesizer, we demonstrated the power of full-screen, syntax-directed iting for block-structured languages, especially when coupled with incre-mental compilation and structured interpretation and debt/gging [Teitelbaum & Reps lg81]. The success of the initial, hand-crated Synthesizer encouraged us to create the Synthesizer Generator, a system for building such environments from language descriptions. At the same time, our gum was to explore methods for integrating additional program analysis and translation tools into interactive program development systems. The desire to enforce context-sensitive syntactic constraints, perform incremental translation, and detect dat~-flow-anomalies implied we needed a way of incorporating knowledge of a languw~e's semantic relations. As argued in our earlier paper [Demers et aL 1981], attribute grammars are an attraetive underlying formalism for systems uch as the Synthesizer Generator because: • They extend the descriptive power of context-fres grammars, thereby permitting expremion of context,-sensitive relationships, such as type consistent T in a program