错误：在'*'标记之前预期'）'

Question

I'm having a problem with the constructor signature in the header below. The compiler gives me the message:

error: expected ')' before '*' token

Can anybody tell me what I might be missing here?

#ifndef PRIORITYQUEUE_H
#define PRIORITYQUEUE_H

#include <iostream>
#include <cstdlib>  //We'll need to use srand() and rand() as well as clock()
#include <ctime>
#include <vector>
#include <list>
#include "Graph.h" //header for Graph class

using namespace std;

class PriorityQueue
{

public:

    PriorityQueue(Graph*):infiniteDist(9999);

    void set_previous_node(int, int);

    int get_node_value(int);

    void set_node_value(int, int);    //Change the node value of an element

    void markVisited(int);

    bool contains(int);   //Does the queue contain a particular vertex?

    void insertIntoQueue(int);

    int top(); //pick an unvisited node with the shortest distance. 

    int queueSize();

    void print();

private:

    class vertexNode {
    public:
        int nodeNum;
        int nodeValue;
        int previousNode;   //previous node visited with shortest distance from source
        bool wasVisited;
    };

    vector<vertexNode> nodeValues;
    const int infiniteDist;          //value to represent infinite distance
    int nodeQuantity;


};

#endif // PRIORITYQUEUE_H

The actual constructor is used as in:

PriorityQueue::PriorityQueue(Graph* graph):infiniteDist(9999)
{
...
}

Answer 1

You are trying to partially declare the constructor by using an initialiser expression, in the declaration of PriorityQueue(Graph*):infiniteDist(9999); . This is not allowed. The declaration (generally in the .h file) should just be:

PriorityQueue(Graph* graph);

The definition (generally in the .cpp file) should then be:

PriorityQueue::PriorityQueue(Graph* graph)
     : infiniteDist(9999)
{
...
}

The reason is simply that the initaliser list is already part of the definition, ie what the method does , rather than just a declaration of the name and return type. Imagine that you'd use a different number (say 42) in the declaration and another (9999) in the definition, which one should be used? Hence it is not allowed.

Answer 2

change this

PriorityQueue(Graph*):infiniteDist(9999);

to

PriorityQueue(Graph*);

Answer 3

PriorityQueue(Graph*):infiniteDist(9999); is wrong.

Either you define your whole constructor in the header 9ie add the body) or you only have to to declare it with PriorityQueue(Graph*);

The solution 2 is the best one.