Operator Precedence Analysis of Expressions

The bottom-up syntax analysis algorithm of chapter 3 handles a subset of programming language arithmetic expressions using a system of numerical priorities. This is the basis of the operator-precedence mechanism. It is one of the oldest forms of syntax analysis, now less popular because it is not as flexible or as good at error detection as the one-track technique nor applicable to as many grammars as the LR (1) technique described in chapter 18, but still very useful in practice in the analysis of expressions of a programming language. It is useful in part because of its efficiency and in part because an operator-precedence analyser can usually be generated direct from the unmodified ‘reference’ grammar for expressions. Its error-processing performance is deficient in theory but with care and some simple pragmatic adjustments it can be made acceptable, given the simple syntactic structure of programming language expressions.