Algorithms in SNOBOL4
A theory of discrete patterns and their implementation in SNOBOL4
Communications of the ACM
The SNOBOL 4 programming language
The SNOBOL 4 programming language
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Quickscan pattern-match mode in SNOBOL4 uses heuristics to determine when it is "impossible" for a pattern match to succeed. Pattern matches ruled hopeless are terminated immediately with failure. An exposition of Quickscan is given in (1). Elaborations of this appear in (2) and (3). This note is intended to set down and clarify three aspects of the Quickscan process. These involve1. the minimum-length assumptions made for each of the fundamental SNOBOL pattern elements2. an exhaustive list of the ways length failure can occur3. the treatment of the pattern element BAL under QuickscanAll assertions here are based on the results of trials run with the macro (or SIL) implementation of SNOBOL4 on an IBM 360. Examples are intended to illustrate the assertions as precisely as possible, and do not represent common or recommended programming practice.