8.11.6.3 IfcDeriveDimensionalExponents（推导量纲指数）

8.11.6.3.1 语义定义（Semantic definition）

ISO/CD 10303-41:1992 标准定义：该函数用于确定单位的量纲指数。对于命名单位，返回其维度属性；对于派生单位，则根据其组成元素计算量纲指数。

参数定义： X：（输入）待推导量纲指数的单位。

8.11.6.3.2 形式化表示（Formal representation）

FUNCTION IfcDeriveDimensionalExponents
    (UnitElements : SET [1:?] OF IfcDerivedUnitElement)
    : IfcDimensionalExponents;  
    LOCAL
    Result : IfcDimensionalExponents :=
            IfcDimensionalExponents(0, 0, 0, 0, 0, 0, 0);  
    END_LOCAL;
    REPEAT i := LOINDEX(UnitElements) TO HIINDEX(UnitElements);
        Result.LengthExponent := Result.LengthExponent +
          (UnitElements[i].Exponent *
           UnitElements[i].Unit.Dimensions.LengthExponent);
        Result.MassExponent := Result.MassExponent  +
          (UnitElements[i].Exponent *
           UnitElements[i].Unit.Dimensions.MassExponent);
        Result.TimeExponent := Result.TimeExponent +
          (UnitElements[i].Exponent *
           UnitElements[i].Unit.Dimensions.TimeExponent);
        Result.ElectricCurrentExponent := Result.ElectricCurrentExponent +
          (UnitElements[i].Exponent *
           UnitElements[i].Unit.Dimensions.ElectricCurrentExponent);
        Result.ThermodynamicTemperatureExponent := Result.ThermodynamicTemperatureExponent +
          (UnitElements[i].Exponent *
           UnitElements[i].Unit.Dimensions.ThermodynamicTemperatureExponent);
        Result.AmountOfSubstanceExponent := Result.AmountOfSubstanceExponent +
          (UnitElements[i].Exponent *
           UnitElements[i].Unit.Dimensions.AmountOfSubstanceExponent);
        Result.LuminousIntensityExponent := Result.LuminousIntensityExponent +
          (UnitElements[i].Exponent *
           UnitElements[i].Unit.Dimensions.LuminousIntensityExponent);
    END_REPEAT;  
    RETURN (Result);

END_FUNCTION;

8.11.6.3.3 参考文献

IfcDerivedUnit