两个连续的减号是什么意思？

[LB4229]

#include <iostream>
#include <conio.h>
using namespace std;

enum Weapons{Pistol, Shotgun, MachineGun, Bazooka, RocketLaucher};

int main(){
	cout <<"Which weapon do you want? "<< endl;
	cout <<"1) Pistal" <<endl;
	cout <<"2) Shotgun" <<endl;
	cout <<"3) Machinegun" <<endl;
	cout <<"4) Bazooka" <<endl;
	cout <<"5) RocketLaucher" <<endl <<endl;

	int weapon_choice;
	cin >> weapon_choice;

	weapon_choice--;//这里带两个减号是什么意思？
	switch(weapon_choice){
	case Pistol:
			cout << "You have chosen a Pistol";
			break;

	case Shotgun:
			cout << "You have chosen a Shotgun";
			break;
	case MachineGun:
			cout << "You have chosen a MachineGun";
			break;
	case Bazooka:
			cout << "You have chosen a Bazooka";
			break;

	case RocketLaucher:
				cout << "You have chosen a RocketLaucher";
				break;

	}
	getch();
	return 0;

}

问下代码里两个连续的减号是什么意思？

[ljt3969636]

weapon_choice--;相当于weapon_choice=weapon_choice-1;
完整滴说int i=weapon_choice--;相当于宣布int i=weapon_choice;然后weapon_choice=weapon_choice-1;
int i=--weapon_choice;相当于先 weapon_choice=weapon_choice-1;然后 int i=weapon_choice;

[LB4229]

这里为什么要减一呀？就用了一次weapon_choice作为switch判断的依据呀

[ljt3969636]

要匹配enum Weapons{Pistol, Shotgun, MachineGun, Bazooka, RocketLaucher};这里枚举类型默认从0开始等价于enum Weapons{0, 1, 2, 3, 4};
而你输入的从1开始：

    cout <<"1) Pistal" <<endl;
    cout <<"2) Shotgun" <<endl;
    cout <<"3) Machinegun" <<endl;
    cout <<"4) Bazooka" <<endl;
    cout <<"5) RocketLaucher" <<endl <<endl;

所以减1啊

[hitaka85]

enum Weapons{Pistol, Shotgun, MachineGun, Bazooka, RocketLaucher};
Pistol=0,Shotgun=1.....

[LB4229]

哦。。。。确实如此，谢谢啦

[pathuang68]

--的含义，1楼说得已经非常清楚了。

enum Weapons{Pistol, Shotgun, MachineGun, Bazooka, RocketLaucher};
// 这个枚举，让：Pistol = 0， Shotgun = 1， MachineGun = 2， Bazooka = 3， RocketLauncher = 4

 int weapon_choice;
 cin >> weapon_choice;

 weapon_choice--;  // 如果你输入的是1， 那么这句话执行完成后weapon_choice就等于0

switch(weapon_choice){
    case Pistol:          // 所以如果你前面输入的是1，就会选择执行这个case
            cout << "You have chosen a Pistol";
            break;

    case Shotgun:     // 所以如果你前面输入的是2，就会选择执行这个case
            cout << "You have chosen a Shotgun";
            break;
    case MachineGun:    // 所以如果你前面输入的是3，就会选择执行这个case
            cout << "You have chosen a MachineGun";
            break;
    case Bazooka:             // 所以如果你前面输入的是4，就会选择执行这个case
            cout << "You have chosen a Bazooka";
            break;

    case RocketLaucher:    // 所以如果你前面输入的是5，就会选择执行这个case
                cout << "You have chosen a RocketLaucher";
                break;

    }

[LB4229]

嗯，明白了，谢谢楼上的，刚才结帖没发现你的回复，不好意思，这次不能给你分了，谢谢你哈