vector_difference

EXPRESS specification:

FUNCTION vector_difference
(* Modified for LPM/6 *)(arg1, arg2 : vector_or_direction) : vector; LOCAL result : vector; res, vec1, vec2 : direction; mag, mag1, mag2 : REAL; ndim : INTEGER; END_LOCAL; IF ((NOT EXISTS (arg1)) OR (NOT EXISTS (arg2))) OR (arg1.dim <> arg2.dim) THEN RETURN (?) ; ELSE BEGIN IF 'STRUCTURAL_FRAME_SCHEMA.VECTOR' IN TYPEOF(arg1) THEN mag1 := arg1.magnitude; vec1 := arg1.orientation; ELSE mag1 := 1.0; vec1 := arg1; END_IF; IF 'STRUCTURAL_FRAME_SCHEMA.VECTOR' IN TYPEOF(arg2) THEN mag2 := arg2.magnitude; vec2 := arg2.orientation; ELSE mag2 := 1.0; vec2 := arg2; END_IF; vec1 := normalise (vec1); vec2 := normalise (vec2); ndim := SIZEOF(vec1.direction_ratios); mag := 0.0; res := dummy_gri || direction(vec1.direction_ratios); REPEAT i := 1 TO ndim; res.direction_ratios[i] := mag1*vec1.direction_ratios[i] + mag2*vec2.direction_ratios[i]; 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( vec1, 0.0); END_IF; END; END_IF; RETURN (result);
END_FUNCTION;