Syntax-Directed Description of Incremental Compilers

Abstract

Program and data structures may be described formally by using graphs with labelled nodes and edges. The Vienna Definition Language [4] is a well-known example of such a system which uses a special type of graphs, namely trees. Implementing an incremental compiler, we must consider various lists and a lot of references between them in order to allow insertion, deletion, or substitution of increments (see e.g. [6]). (We consider increments to be some syntactical units still to be defined by the implementer.) Formally, these data constitute a graph with labelled nodes (increments and some special “nonterminal” symbols, e.g. pointers) and labelled edges (references of different types); however, the result is not always a tree. We may consider the following types of edges: surrounding block of an increment or block, applied occurrence of a declared entity, next increment, first increment of a block, etc. Establishing a syntax-directed concept for implementing incremental compilers, we need a formal system to describe the syntax of languages the words of which are labelled graphs.