[Oberon] System V5 - Definitions and Implementations

[thomas.kral at email.cz]

Hi,

I found this example in Programming in Oberon (PIO) book. The PO 2013 project documentation uses Definitions frequently to describe various system functionality, it is easy for the reader to follow concepts without need to understand all details of Implementation. 

It is a very descriptive aid for documenting, however how can Definitions be used from a programmer's point of view?

DEFINITION Buffer;
 VAR nonempty, nonfull: BOOLEAN;
 PROCEDURE put(x: INTEGER);
 PROCEDURE get(VAR x: INTEGER);
END Buffer.

MODULE Buffer; (*cyclic buffer of integers*)
 CONST N = 100;
 VAR nonempty*, nonfull*: BOOLEAN;
   in, out, n: INTEGER;
   buf: ARRAY N OF INTEGER;
  PROCEDURE put*(x: INTEGER);
  BEGIN
   IF n < N THEN
      buf[in] := x; in := (in+1) MOD N;
      INC(n); nonfull := n < N; nonempty := TRUE
   END
  END put;
  PROCEDURE get*(VAR x: INTEGER);
  BEGIN
   IF n > 0 THEN
      x := buf[out]; out := (out+1) MOD N;
      DEC(n); nonempty := n > 0; nonfull := TRUE
   END
  END get;
BEGIN (*initialize*) n := 0; in := 0; out := 0;
 nonempty := FALSE; nonfull := TRUE
END Buffer.

Many thanks Tomas