A forward move algorithm for LL and LR parsers

Abstract

A wide variety of algorithms have been suggested for the repair of syntactic errors in a computer program. Since there is usually more than one possible repair for any syntax error, many algorithms employ a cost function to guide the the repair, and some [1,3,4,6], guarantee that the repair chosen will be least-cost, according to some definition. (The others, although guided by costs, do not guarantee least-cost in all cases.) Fischer et al. [4,6,7] define a “locally least-cost” repair using insertions and deletions, and provide algorithms for LL and LR parsers. A locally least-cost repair is a least-cost sequence of deletions and insertions such that one more symbol in the original string will be accepted by the parser. Backhouse [2,3] uses a similar definition. In both cases, the repair algorithms operate by examining a single symbol in the input at any time.