MODULE grep0;
(*---------------------------------------------------------
File name: grep0.pm
Author: AG
Date: 10/06/05 

Problem: Find a pattern of characters on a chain. Pattern is 
originally stored in an array.

Example of Execution:

Pattern: abcd
 L3ch  :       abcd      ...

 L2ch  :  cddabcdbbedddddadaedacabacbeadeaddcbe...eee

 Total found:   5
Cycles:
N selections + N MOVE + N select + 2N assignments

IMPORTANT:
N is the size of the pattern, not the size of the chain.

*)
(*----------------------------------------------------------					
		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 
		L1bool: 		chain OF INTEGER;
		Achar:		ARRAY[0..(N-1)] OF CHAR;	
		L2ch, L3ch:	chain OF CHAR;
		i, RightLimit, Tot: INTEGER;
		StartChar, nChar: INTEGER;
		
(*--------------------------------------------------------
		MAIN
-----------------------------------------------------------*)
BEGIN
	(* initializing data *)
	RightLimit:= 100;
	StartChar:= 97;	(* ascii code for where the lower case alphabet starts *)
	nChar:= 5;	(* number of characters (total = 25) *)
	L2ch := CHR((RandomInt(chain) MOD nChar) + StartChar);
	Achar[0] := 'a';
	Achar[1] := 'b';
	Achar[2] := 'c';
	Achar[3] := 'd';
	
	(* ==================start algorithm======================= *)
	L1bool:= 1;		(* initialize chain to test all *)
	FOR i:= 0 TO (N - 1) DO 
		IF L1bool = 1 THEN	(* if selected *)
			IF L2ch # Achar[i] THEN		(* if not there*)
				L1bool := 0;		(* deselect *) 
			END; (* IF *)
		END; (* IF *)
		L1bool := MOVE.right(L1bool);	(* shift for next item *)
	END; (* for *)
	Tot:= REDUCE.SUM(L1bool);	(* get total found *)
	
	(* to get the result *)
	L1bool:= MOVE.left(L1bool);
	FOR i:= 0 TO (N-1) DO
		IF L1bool = 1 THEN
			L3ch:= L2ch;	(* pass on to chek line *)
			SEND.left(L1bool, L1bool);	(* send the marker left *)
		END; (* IF *)
	END; (* FOR *)
		(* count 1's= how many times found*)
	
	
	(*================== printing========================== *)	
	
	WriteString("Pattern: ");
	FOR i:= 0 TO (N - 1) DO
		Write(Achar[i]);
	END; (* FOR *) WriteLn;
	WriteString( " L3ch  :  ");Write( L3ch); WriteLn;
	WriteString( " L2ch  :  ");Write( L2ch); WriteLn;
	WriteString( " Total found:  ");WriteInt(Tot ,  2); WriteLn;
END grep0.