FUNCTION cross_product

(* SCHEMA STRUCTURAL_FRAME_SCHEMA; *)

(* Modified for LPM/6 *)
FUNCTION cross_product
	(arg1, arg2 : direction) : vector;
  LOCAL
    mag    : REAL;
    res    : direction;
    v1,v2  : LIST[3:3] OF REAL;
    result : vector;
  END_LOCAL;
  
  IF ( NOT EXISTS (arg1) OR (arg1.dim = 2)) OR
     ( NOT EXISTS (arg2) OR (arg2.dim = 2)) THEN
    RETURN(?);
  ELSE
    BEGIN
      v1  := normalise(arg1).direction_ratios;
      v2  := normalise(arg2).direction_ratios;
      res := dummy_gri || direction([(v1[2]*v2[3] - v1[3]*v2[2]),
            (v1[3]*v2[1] - v1[1]*v2[3]), (v1[1]*v2[2] - v1[2]*v2[1])]);
      mag := 0.0;
      REPEAT i := 1 TO 3;
        mag := mag + res.direction_ratios[i]*res.direction_ratios[i];
      END_REPEAT;
      IF (mag > 0.0) THEN
        result := dummy_gri || vector(res, SQRT(mag));
      ELSE
        result := dummy_gri || vector(arg1, 0.0);
      END_IF;
      RETURN(result);
    END;
  END_IF;
END_FUNCTION;  (*  STEP Part 42 (modified in 2nd edition)  *)

Referenced By

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2023-03-25T00:11:39-04:00