MODULE checkid;
(*---------------------------------------------------------
File name: checkid.pm
Author: AG
Date: 6/07/05 

Problem: This program cheks if an ARRAY of of chains of size N 
contains an identity matrix for N x N.

Example of Execution 1:
	ArrLine[0]: 1  0  0  0  1  0  0  0  1  0  0  0  1  0  0
	ArrLine[1]: 0  1  0  0  0  1  0  0  0  1  0  0  0  1  0
	ArrLine[2]: 0  0  1  0  0  0  1  0  0  0  1  0  0  0  1
	ArrLine[3]: 0  0  0  1  0  0  0  1  0  0  0  1  0  0  0
	Res:TRUE

Example of Execution 2:
	ArrLine[0]: 1  0  0  0  1  0  0  0  1  0  0  0  1  0  0
	ArrLine[1]: 0  1  0  0  0  1  0  0  0  1  0  0  0  1  0
	ArrLine[2]: 0  0  1  1  0  0  1  0  0  0  1  0  0  0  1
	ArrLine[3]: 0  0  0  1  0  0  0  1  0  0  0  1  0  0  1
	Res:FALSE

Cycles:
1 Shift + 1 ID + 4 assignments + 3 tests.
*)
(*----------------------------------------------------------
		CONFIGURATION
----------------------------------------------------------*)
CONST  MAXCELLS=1024; (* MAXCELLS cells in one line *)
CONST N=4;

CONFIGURATION chain[0..(MAXCELLS - 1)];
CONNECTION
		left: chain [i] -> chain[(i-1) MOD MAXCELLS];
		right: chain[i] -> chain[(i+1) MOD MAXCELLS];
(*----------------------------------------------------------
		VARIABLES
----------------------------------------------------------*)
VAR 
		L1: chain OF INTEGER;
		i:INTEGER;
		Res: BOOLEAN;
		ArrLine: ARRAY[0..(N-1)] OF chain OF INTEGER;
(*----------------------------------------------------------
		MAIN
----------------------------------------------------------*)
BEGIN
	(* initialize data *)
(*---------------------------------------------------------
		GENERATE IDENTITY MATRIX FOR TEST
		file: genidn.pm
----------------------------------------------------------*) 
	L1:= 0;
	
	(*generate master line *)
	IF ID(chain) MOD N = 1 THEN
		L1:= 1;			(* Put a 1 every N element *)
	END; (* IF *)
	ArrLine[0]:= L1;	(* copy master line into first line *)
	
	(* generate other lines *)
	FOR i:= 1 TO (N-1) DO 
		ArrLine[i] := RECEIVE.right(ArrLine[i-1]); (* shift by one on every following array *)
	END; (*FOR*)
	(* ArrLine[2]<< 4>> := 1; TO MAKE FALSE *)
	
	(* Printing *)
	IF ID(chain) < 16 THEN
		FOR i:= 0 TO (N-1) DO
			WriteString("ArrLine["); WriteInt(i, 0); WriteString("]:"); 
			WriteInt(ArrLine[i], 2); WriteLn;
		END; (*FOR*)
	END; (* display *)
(*---------------------------------------------------------
		START ALGORITHM
----------------------------------------------------------*)
	(* generate master line  for N = 4 , L1 = 1 0 0 0 1 0 0 0 1 0 0 0 1.. *)
	L1:= 0;
	IF ID(chain) MOD N = 1 THEN
		L1:= 1;			(* Put a 1 every N element *)
	END; (* IF *)
	
	Res:= TRUE;
	FOR i:= 0 TO (N-1) DO
		IF ArrLine[i] # L1 THEN
			Res := FALSE;
		END; (* IF *)
		L1 := MOVE.right(L1);
	END; (* FOR *)
	
	(* printing *)
	WriteString("Res:" ); WriteBool(Res, 2); WriteLn;
END checkid.