专门化模板化的内部模板 class
Specializing inner template of templated class
所以我有一个模板图像 class，我正在尝试为其设置内联颜色转换。这是让我烦恼的代码的简化：
template <typename Color = colors::RGB>
class Image {
/// ...
template <typename DestColor>
operator Image<DestColor>() {
/// when assigning with a different colorspace:
/// ... do the color conversion
/// ... and return a fresh Image<DestColor>
}
template <>
operator Image<Color>() {
/// when assigning with the same colorspace:
return *this;
}
};
…问题是模板化转换运算符后面的模板特化不能在class级别定义（根据我得到的错误）。
我知道需要离线指定专业化，但我一辈子都搞不懂语法。我应该如何申报该专业？
只需删除专业化。如果 DestColor 与 Color 相同，您的转换函数将永远不会被调用。 [class.conv.fct]/p1:
A conversion function is never used to convert a (possibly
cv-qualified) object to the (possibly cv-qualified) same object type
(or a reference to it), to a (possibly cv-qualified) base class of
that type (or a reference to it), or to (possibly cv-qualified)
void.
所以我有一个模板图像 class，我正在尝试为其设置内联颜色转换。这是让我烦恼的代码的简化：
template <typename Color = colors::RGB>
class Image {
/// ...
template <typename DestColor>
operator Image<DestColor>() {
/// when assigning with a different colorspace:
/// ... do the color conversion
/// ... and return a fresh Image<DestColor>
}
template <>
operator Image<Color>() {
/// when assigning with the same colorspace:
return *this;
}
};
…问题是模板化转换运算符后面的模板特化不能在class级别定义（根据我得到的错误）。
我知道需要离线指定专业化，但我一辈子都搞不懂语法。我应该如何申报该专业？
只需删除专业化。如果 DestColor 与 Color 相同，您的转换函数将永远不会被调用。 [class.conv.fct]/p1:
A conversion function is never used to convert a (possibly cv-qualified) object to the (possibly cv-qualified) same object type (or a reference to it), to a (possibly cv-qualified) base class of that type (or a reference to it), or to (possibly cv-qualified)
void.