[英]c++11 inheriting template constructors
I find the syntax of the constructor inheritance slightly odd. 我发现构造函数继承的语法略显奇怪。 The example below works well, but I do not understand why I need to specify using sysTrajectory::sysTrajectory
and not using sysTrajectory<Real>::sysTrajectory<Real>
when inheriting from a class template? 下面的示例运行良好,但我不明白为什么我需要using sysTrajectory::sysTrajectory
指定并且在从类模板继承时不using sysTrajectory<Real>::sysTrajectory<Real>
? The latter gives the following error: expected ';' before '<' token using sysTrajectory<Real>::sysTrajectory<Real>;
后者给出以下错误: expected ';' before '<' token using sysTrajectory<Real>::sysTrajectory<Real>;
expected ';' before '<' token using sysTrajectory<Real>::sysTrajectory<Real>;
. 。
class sysRealTrajectory: public sysTrajectory<Real>
{
public:
/**
* Default constructor
*/
inline sysRealTrajectory(void);
using sysTrajectory::sysTrajectory;
/**
* Default destructor
*/
inline ~sysRealTrajectory(void);
};
main : 主要:
Real a;
a=5;
sysTrajectoryPoint<Real> TP0(1.0,a);
sysRealTrajectory Trajectory(TP0);
This syntax 这个语法
using sysTrajectory::sysTrajectory;
Names all constructors of sysTrajectory
. 命名sysTrajectory
所有构造sysTrajectory
。 This syntax 这个语法
using sysTrajectory::sysTrajectory<Real>;
Names only a constructors that accept a template argument <Real>
(yes, you can do that, you can pass explicit template arguments to constructors in declarative contexts). 仅命名接受模板参数<Real>
的构造函数(是的,您可以这样做,您可以将显式模板参数传递给声明性上下文中的构造函数)。 Your base class does not appear to have any constructor templates, so your compiler's parser does not take sysTrajectory
as a template-name and hence does not accept the <
as an opening template argument list. 您的基类似乎没有任何构造函数模板,因此编译器的解析器不会将sysTrajectory
作为模板名称,因此不接受<
作为开放模板参数列表。 Hence the syntax error. 因此语法错误。
For a template-name to be explicitly qualified by the template arguments, the name must be known to refer to a template. 对于要由模板参数显式限定的模板名称,必须知道名称才能引用模板。
Even if you had a constructor template, a rule for using declarations forbids that too. 即使你有一个构造函数模板,使用声明的规则也禁止这样做。 It says 它说
A using-declaration shall not name a template-id. using声明不应命名template-id。
在gcc 4.8.1中,以下语法适用于我:
using sysTrajectory<Real>::sysTrajectory;
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