INTERFACE PZIntChain;

IMPORT Rd, Wr; 

TYPE
  Point = ARRAY [0..1] OF INTEGER;
  T = ARRAY OF Point;

PROCEDURE Trim(READONLY c: T; start, length: CARDINAL): REF T;
  (*
    Returns a new chain that is a copy of elements from "c[start]"
    to "c[start+length-1]".  Assumes the chain is periodic, i.e.
    "c[i+n]=c[i]" for all "i", where "n=NUMBER(c)".  *)

TYPE
  ReadData = RECORD cmt: TEXT; c: REF T END;
    
PROCEDURE Write(wr: Wr.T; cmt: TEXT; READONLY c: T);
 
PROCEDURE Read(rd: Rd.T): ReadData;

END PZIntChain.