----------------------------------------
            TurboPower Utilities Programmer's Manual
                           RPL Utility
            ----------------------------------------
             Copyright (C) 1985 TurboPower Software.
                      All Rights Reserved.


1. Introduction

RPL is based on the pattern matching algorithms presented in the
book "Software Tools in Pascal". However, we have significantly
extended the capabilities of the tools presented there, and have
also used more of the powerful data structures available in
Pascal to improve the performance of the program.

We are very interested in hearing of any general purpose
match/replace expressions that you develop using RPL.


2. Algorithms

For a basic introduction to regular expressions or pattern
matching algorithms we direct you to the references given in
section 6.

RPL uses a record and pointer-based approach to storing regular
expressions. The following type declarations are key to all of
the operations of RPL.

  TYPE
    longstring = string[255];

    tokens = (tnil, tlitchar, tccl, tnccl, tclosure, tmaybeone,
              tany, tbol, teol, tgroup, tbtag, tetag, tditto);

    patptr = ^patrecord;

    sptr = ^longstring;

    patrecord = RECORD
                  tok : tokens;
                  one : Char;
                  nextok : Boolean;
                  strptr : sptr;
                  nestptr, next : patptr;
                END;

Each regular expression used by RPL is stored internally as a
linked list of PATRECORDs. The function of each record is
described by the .TOK field of the record. The most
straightforward function for one of these records is the TLITCHAR
token type. This indicates that the record will match a single
literal character, and that character is stored in the .ONE field
of the record. The record fields perform the following functions:

   TOK - a scalar type that classifies the function of this
         regular expression token.

   ONE - a single character, only used when the token