Example of Jensen's Device
	CSc 404 Documentation And Examples

begin
    comment This is a simple example of Jensen's device;

    comment This takes the sum of expr from start to stop, inclusive.
        The variable index is incremented through the range.;
    real procedure sumof(start, stop, index, expr);
        value start, stop;
        integer start, stop, index;
        real expr;
        begin
            real sum;

            comment initialize sum to zero and add the terms.;
            sum := 0.0;
            for index := start step 1 until stop do begin
                sum := sum + expr
            end;

            sumof := sum
        end;

    begin
        comment Sum of integers, 1 to 10.;
        integer i;
        outreal(1, sumof(1, 10, i, i));
        outstring(1, "\n");
    end;

    begin
        comment sum of squares, -5 to 5.;
        integer j;
        outreal(1, sumof(-5, 5, j, j*j));
        outstring(1, "\n");
    end;
end