ZPL: an array oriented parallel language

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  1. Array oriented, parallel execution, compiler language.
  2. Example: Take gradient of nearest four neighbours. 

    -- Sample ZPL program
program Grad4nbr;

prototype GetImageSize(infile:file):integer;

config var
		m	: integer = GetImageSize(zin);
		n	: integer = GetImageSize(zin);
		ofname  : string = "output.pnm";

region		IM = [1..n, 1..m];
var		A, B : [IM] integer;

direction	north = [-1, 0];
		east  = [ 0, 1];
		west  = [ 0,-1];
		south = [ 1, 0];

-- Fake ASCII format of PGM(Portable Gray Map)
procedure OutImage(outfile:file; var X : [IM] integer);
begin
	writeln(outfile, "P2");
	writeln(outfile, m, " ", n);
	writeln(outfile, 255);
 [IM]	writeln(outfile, X);
end;

procedure GetImageSize(infile:file):integer;
var dim:integer;
begin
	read(infile,dim);
	writeln(zerr, "Read size = ", dim);
	return dim;
end;

procedure Grad4nbr();
var outfile : file;
begin

  [IM]	 	read(zin, A);
  [north of IM]	reflect A;
  [east of IM]	reflect A;
  [west of IM]	reflect A;
  [south of IM]	reflect A;

  [IM]		B := 255 - max(max(abs(A - A@north),
				   abs(A - A@east)),
			       max(abs(A - A@west),
				   abs(A - A@south)));

		outfile := open(ofname, "w");
		OutImage(outfile, B);
		close(outfile);
end;

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