【c++构造函数】请问为什么报错啊？

似乎是构造函数不对，但是看不出来哪里不对。

****head.h****
#include<iostream>
template<class type>
class seqlist {
public:
    seqlist(int size){
        maxsize = size;
        length = 0;
        start = new type[maxsize];
    }
    seqlist(std::istream& in) { read(in); }
    ~seqlist() { delete[]start; }
    std::istream& read(std::istream&);
    void simplify();
    void cancel(int);
    void output(std::ostream&);
private:
    type* start;
    int maxsize, length;
};

**head.cpp**
#include"head.h"
#include<iostream>
using namespace std;
template<class type> istream& seqlist<type>::read(istream& in) {
    cout << "please input the length of the list:";
    in >> maxsize;
    start = new type[maxsize];
    type x;
    length = 0;
    while (in >> x) {
        *start++ = x;
        length++;
    }
    return in;
}
template<class type> void seqlist<type>::cancel(int i) {
    for (; i < length - 1; i++)
        start[i] = start[i + 1];
}

template<class type> void seqlist<type>::simplify() {
    for(int i=0;i<length;i++)
        for (int j = i + 1; j < length; j++) {
            if (start[i] == start[j])
                cancel(j);
        }
}

template<class type> void seqlist<type>::output(ostream& out) {
    for (int i = 0; i < length; i++)
        out << start[i] << " ";
}

**main.cpp**
#include"head.h"
#include<iostream>
using namespace std;
int main() {
    seqlist<int> data(cin);
    data.simplify();
    data.output(cout);
}

给出了什麽错误提示信息啊？