我有一种直觉VS2012在这一个上是错误的,但我不确定。程序在Visual Studio 2012中运行,但不是ideone.com
看过this question之后,我觉得想要实现类似的东西。
我的版本在Visual Studio 2012上工作正常,但是甚至没有在Ideone上编译。
这里是我的主界面:
#include <iostream>
#include <string>
template <class In, class Out>
struct Pipe
{
typedef In in_type ;
typedef Out out_type ;
In in_val ;
Pipe (const in_type &in_val = in_type()) : in_val (in_val)
{
}
virtual auto operator()() const -> out_type
{
return out_type() ;
}
};
template <class In, class Out, class Out2>
auto operator>> (const Pipe <In, Out> &lhs, Pipe <Out, Out2> &rhs) -> Pipe <Out, Out2>&
{
rhs = lhs() ;
return rhs ;
}
template <class In, class Out>
auto operator>> (const Pipe <In, Out> &lhs, Out &rhs) -> Out&
{
rhs = lhs() ;
return rhs ;
}
这里有几个测试类:
struct StringToInt : public Pipe <std::string, int>
{
StringToInt (const std::string &s = "") : Pipe <in_type, out_type> (s)
{
}
auto operator()() const -> out_type
{
return std::stoi (in_val) ;
}
};
struct IntSquare : public Pipe <int, int>
{
IntSquare (int n = 0) : Pipe <in_type, out_type> (n)
{
}
auto operator()() const -> out_type
{
return in_val * in_val ;
}
};
struct DivideBy42F : public Pipe <int, float>
{
DivideBy42F (int n = 0) : Pipe <in_type, out_type> (n)
{
}
auto operator()() const -> out_type
{
return static_cast <float> (in_val)/42.0f ;
}
};
和这里的司机:
int main()
{
float out = 0 ;
StringToInt ("42") >> IntSquare() >> DivideBy42F() >> out ;
std::cout << out << "\n" ;
return 0 ;
}
Ideone抱怨模板扣除和其无法找到正确的operator>>
候选功能:
prog.cpp: In function ‘int main()’:
prog.cpp:75:21: error: no match for ‘operator>>’ (operand types are ‘StringToInt’ and ‘IntSquare’)
StringToInt ("42") >> IntSquare() >> DivideBy42F() >> out ;
^
prog.cpp:75:21: note: candidates are:
prog.cpp:23:6: note: Pipe<Out, Out2>& operator>>(const Pipe<In, Out>&, Pipe<Out, Out2>&) [with In = std::basic_string<char>; Out = int; Out2 = int]
auto operator>> (const Pipe <In, Out> &lhs, Pipe <Out, Out2> &rhs) -> Pipe <Out, Out2>&
^
prog.cpp:23:6: note: no known conversion for argument 2 from ‘IntSquare’ to ‘Pipe<int, int>&’
prog.cpp:30:6: note: template<class In, class Out> Out& operator>>(const Pipe<In, Out>&, Out&)
auto operator>> (const Pipe <In, Out> &lhs, Out &rhs) -> Out&
^
prog.cpp:30:6: note: template argument deduction/substitution failed:
prog.cpp:75:35: note: deduced conflicting types for parameter ‘Out’ (‘int’ and ‘IntSquare’)
StringToInt ("42") >> IntSquare() >> DivideBy42F() >> out ;
哪个编译器是正确的?如果Ideone是正确的,是否有任何简单的解决这个代码?
与(*可能重复?*)相关:[非常量引用绑定到临时的Visual Studio错误?](http://stackoverflow.com/q/16380966/1708801)...基本上gcc在这里是正确的。如果在Visual Studio中使用'/ Za'构建,它也会失败,[请参阅此链接](http://rextester.com/GYMOJ23021)。 – 2014-10-07 20:36:17
这是愚蠢的投票结束这个问题,因为*为什么不是这个代码工作*。测试可能会更小,但它是一个完整的测试用例,编译器之间的结果相互矛盾,并且对于大多数人来说这肯定不明显。 – 2014-10-07 20:43:37