我正在尝试为operator<<
课程重载Graph
,但我一直遇到各种错误:
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
error C2143: syntax error : missing ',' before '<'
我将operator<<
的原型放在Graph
类定义的正上方。 operator<<
的定义位于文件的最底部。这些错误是否与标题保护有关?
这是Graph.h
:
#ifndef GRAPH
#define GRAPH
#include <iostream>
#include <vector>
#include <map>
#include <sstream>
#include "GraphException.h"
#include "Edge.h"
using namespace std;
template <class VertexType>
ostream& operator<<( ostream& out, const Graph<VertexType>& graph );
/** An adjacency list representation of an undirected,
* weighted graph. */
template <class VertexType>
class Graph
{
friend ostream& operator<<( ostream& out, const Graph& graph );
// stuff
}
template <class VertexType>
ostream& operator<<( ostream& out, const Graph<VertexType>& graph )
{
return out;
}
#endif GRAPH
这里是main
:
#include <iostream>
#include "Graph.h"
using namespace std;
const unsigned MAX_NUM_VERTICES = 9;
int main()
{
// create int graph:
Graph<int> iGraph( MAX_NUM_VERTICES );
// add vertices and edges
cout << iGraph;
return 0;
}
答案 0 :(得分:0)
operator<<
的声明缺少Graph
的声明。一种解决方案是在operator<<
声明之前声明类:
template <class VertexType>
class Graph;
或者你可以完全省略课堂外operator<<
的声明,因为friend
声明也构成operator<<
的非成员声明。