问题描述
此代码按预期编译和工作(它在运行时抛出,但不介意):
This code compiles and works as expected (it throws at runtime, but never mind):
#include <iostream>
#include <boost/property_tree/ptree.hpp>
void foo(boost::property_tree::ptree &pt)
{
std::cout << pt.get<std::string>("path"); // <---
}
int main()
{
boost::property_tree::ptree pt;
foo(pt);
return 0;
}
但是一旦我添加模板并更改 foo
原型到
But as soon as I add templates and change the foo
prototype into
template<class ptree>
void foo(ptree &pt)
我在GCC中遇到错误: p>
I get an error in GCC:
test_ptree.cpp: In function ‘void foo(ptree&)’:
test_ptree.cpp:7: error: expected primary-expression before ‘>’ token
但没有MSVC ++的错误!错误在标记行< ---
中。再次,如果我把问题行改成
but no errors with MSVC++! The error is in the marked line <---
. And again, if I change the problem line into
--- std::cout << pt.get<std::string>("path"); // <---
+++ std::cout << pt.get("path", "default value");
错误消失(问题在于显式< std :: string> ;
)。
the error disappears (the problem is in explicit <std::string>
).
要求Boost> = 1.41。请帮助我理解并修复此错误。
Boost.PropertyTree requires Boost >= 1.41. Please help me to understand and fix this error.
请参阅
See Templates: template function not playing well with class’s template member function — a similar popular question containing other good answers and explanations.
推荐答案
您需要执行以下操作:
std::cout << pt.template get<std::string>("path");
使用模板
(也就是说,由于 pt:code> typename
:get 是模板成员对模板参数的依赖,你需要告诉编译器它是一个模板。)
(That is, since pt::get
is a template member dependent on a template parameter, you need to tell the compiler it's a template.)
这篇关于C ++模板编译错误:'>'令牌之前的预期主表达式的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!