为何输出函数返回值全是为1？

Question

问题遇到的现象和发生背景

C++，使用CodeBlocks，为何在函数内输出和函数外输出结果不一样？

问题相关代码，请勿粘贴截图

//sport.h
#ifndef SPORT_H
#define SPORT_H
class sport{
private:
    double position;
    double velocity;
    double acceleration;
public:
    void setAcceleration(double tmp);
    void setVelocity(double tmp);
    void setPosition(double tmp);
    double getPosition() const;
    double getVelocity() const;
    double getAcceletation() const;
};
#endif // SPORT_H

//sport.cpp
#include "sport.h"
void sport::setPosition(double p)
{
    position = p;
}

void sport::setVelocity(double v)
{
    velocity = v;
}

void sport::setAcceleration(double a)
{
    acceleration = a;
}

double sport::getAcceletation()const
{
    return acceleration;
}

double sport::getPosition()const
{
    return position;
}

double sport::getVelocity()const
{
    return velocity;
}

//main.cpp
#include <iostream>
#include "sport.h"
#include <iomanip>
using namespace std;

double A_V(sport &obj,double t)
{
    double k = 1;
    double stime,tmp_v,tmp_a;
    stime = t;

    tmp_v = obj.getVelocity() + obj.getAcceletation() * stime;

    tmp_a = - k * tmp_v;

    obj.setAcceleration(tmp_a);
    obj.setVelocity(tmp_v);
    return tmp_v;
}

double X_V(sport &obj,double t)
{
    double tmp_p,tmp_v,stime;
    stime = t;
    tmp_v = obj.getVelocity();

    tmp_p = obj.getPosition() + tmp_v * stime;
    obj.setPosition(tmp_p);
    return tmp_p;
}

int main()
{
    sport obj;
    obj.setVelocity(1);
    obj.setPosition(0);
    obj.setAcceleration(-1);
    double t = 0.01,x = 0;

    for(int i=0;i<1/t;i++)
    {
        x = x + t;
        A_V(obj,t);
        X_V(obj,t);
        cout << X_V <<endl;
    }
    return 0;
}

//

运行结果及报错内容

输出结果全为 1

我的解答思路和尝试过的方法

main函数输出处改为

 cout << obj.getPosition() <<endl;

或在X_V( )函数中添加代码

 cout <<tmp_p<<endl;

则结果正确

我想要达到的结果

为什么会出现这种现象？

Answer 1

46行输出的X_V是啥东西，你到底想输出什么？