(* Chapter 3: file README03.p *)

Pascal code for Chapter 3 of

Programming Languages: Concepts and Constructs,
by Ravi Sethi, Addison Wesley, 1996

The files are

    uniq.p
    table.p


-------------------------------------------------------------------
FILE:    uniq.p
PROGRAM: uniq
PURPOSE: illustrates informal use of invariants for program design
SEE:     Section 3.1, pages 62-63; FIgure 3.4, page 68
COMMENT: The program removes adjacent duplicates.

         The evolution of imperative languages from assembly
         language to Pascal is illustrated by a sequence of
         programs for removing adjacent duplicates from a list
         of elements. The first such is a RAM program in Chapter 1
         (see file README01.p and the code for Chapter 1).

         Chapter 4 (see README04.p) contains a program that allows
         list elements to be bibliographic entries.  All operations
         on such lists have to be programmed explicitly using
         procedures.

         With the input

            1 1 2 2 2 3 1 4 4 0

         program uniq produces the output

                 1
                 2
                 3
                 1
                 4

-------------------------------------------------------------------
FILE:    table.p
PROGRAM: table
PURPOSE: Uses the linear search fragment developed in Section 3.5
SEE:     pages 82-86
COMMENT: The program reads a list of integers and writes out
         an integer if is seen for the first time.  Thus, it
         removes duplicates, not just adjacent duplicates.
         The program fragment for linear search developed
         in Section 3.5 forms the body of function find in
         program table, a program created simply to test
         the code for linear search.

         Program table reads a list of integers and writes
         out an integer if it has not already appeared in
         the list.  With input

         1 1 2 2 2 3 1 4 4 0

         program table produces the output

                 1
                 2
                 3
                 4

-------------------------------------------------------------------