C ++模板歧义

本文介绍了C ++模板歧义的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我和一个朋友正在讨论C ++模板.他问我该怎么办:

A friend and I were discussing C++ templates. He asked me what this should do:

#include <iostream> template <bool> struct A { A(bool) { std::cout << "bool\n"; } A(void*) { std::cout << "void*\n"; } }; int main() { A<true> *d = 0; const int b = 2; const int c = 1; new A< b > (c) > (d); }

main的最后一行有两个合理的解析.是'b'是模板参数还是b > (c)是模板参数?

The last line in main has two reasonable parses. Is 'b' the template argument or is b > (c) the template argument?

尽管，将其编译并查看我们得到的结果是微不足道的，但我们想知道是什么解决了歧义?

Although, it is trivial to compile this, and see what we get, we were wondering what resolves the ambiguity?

推荐答案

AFAIK，它将被编译为new A<b>(c) > d.这是解析它的唯一合理的方法恕我直言.如果解析器在正常情况下不能假设>结束模板参数，那将导致更多的歧义.如果您希望以其他方式使用它，则应编写:

AFAIK it would be compiled as new A<b>(c) > d. This is the only reasonable way to parse it IMHO. If the parser can't assume under normal circumstances a > end a template argument, that would result it much more ambiguity. If you want it the other way, you should have written:

new A<(b > c)>(d);