如何将点添加到结构类型的向量

Question

I am trying to add points(vertices) to a vector of struct type. I am a beginner and I know I can use push_back. But I keep getting three errors:

• no appropriate default constructor available
• left of '.push_back' must have class/struct/union
• expression must have class type.

What I am doing wrong? Here's my code...

#include "stdafx.h"
#include <vector>
#include <iostream>
#include <math.h>
using namespace std;

struct Points
{
    int x, y;
    Points(int paramx, int paramy) : x(paramx), y(paramy) {}  
}p1,p2;

vector <Points> pointes();

void addPoint(int a, int b);
void directionPoint(Points p1, Points p2);

int main()
{
    return 0;
}

void addPoint(int x, int y)
{
    pointes.push_back(Points(x, y));    
}

void directionPoint(Points p1, Points p2)
{  
    if ((p1.x*p2.y - p2.x*p1.y) > 0)
    {
        cout << "direction is anticlockwise" << endl;
    }
    else
        cout << "direction is clockwise" << endl;
}

Answer 1

std::vector doesn't require its value type to be default-constructible. The reasons for compile errors are different:

struct Points
{
  //...
}p1,p2;

You declare p1 and p2 with no arguments. To do that struct Points must have a default constructor. You have to either remove them or specify arguments for the constructor.

Also,

vector <Points> pointes();

This declares a function pointes taking no arguments and returning vector<Points> . Declare it just as vector <Points> pointes;

After these two changes the code compiles: Demo

Answer 2

The error no appropriate default constructor available is caused by your code

} p1,p2;

This can be corrected by either creating an appropriate constructor in your struct, removing these values if not needed, or using the existing constructor:

} p1(0,0),p2(0,0);

The left of '.push_back' must have class/struct/union and expression must have class type error is caused by

vector <Points> pointes();

To correct it remove the parenthesis:

vector <Points> pointes;