可能重复:
非推断上下文的解决方法
GCC 无法推断此“简单”函数的参数。有什么方法可以帮助编译器吗?
template<int a> struct A
{
template<int b> struct B
{
};
};
template<int a, int b> void test(typename A<a>::template B<b> param) { }
int main()
{
A<1>::B<2> b;
test<1,2>(b); // works
test(b); // doesn't work
}
来自 GCC 4.7.1 的错误消息:
test.cpp: In function 'int main()':
test.cpp:15:8: error: no matching function for call to 'test(A<1>::B<2>&)'
test.cpp:15:8: note: candidate is:
test.cpp:8:29: note: template<int a, int b> void test(typename A<a>::B<b>)
test.cpp:8:29: note: template argument deduction/substitution failed:
test.cpp:15:8: note: couldn't deduce template parameter 'a'