Chapter 10 - STRING PROCESSING

Abstract

This chapter discusses the string processing. Character strings are the base of all word processing, text processing, and language processing. As everything gets expressed in some form of language, one may rightfully say that all data is reducible to character strings. This shows that all processes are string processes. Most of the conventional languages offer little or no support of strings either in representing them or manipulating them or both. PL1 was an exception, but it did not go as far as it could have. A string is defined as a sequence of characters that has a varying length and may grow or diminish in any way. The only size limit is of a physical nature, not of a logical nature. The important thing about a string is that it usually has an internal structure, which is significant and, thus, needs to be explored. A string may have any structure of a given set of possible structures. Thus, there are three operations that are needed: (1) verify that a string has a certain structure; (2) extract some structural part of a string; (3) and replace some structural part of a string. These operations are primitive and indispensable. The structure a string may have is always describable by syntax rules of some phrase structure grammar.