# 在 VEXcode Pro V5 中编写返回一个值的函数

## 示例：一个简单的最大公分母(GCD)函数(使用欧几里得算法)

### 不使用用户定义的函数：

```int main() {
int remainder = 1;
int a1, b1, a2, b2;
vexcodeInit();
a1 = a2 = 20;
b1 = b2 = 64;
while(remainder > 0){
remainder = a1 % b1;
a1 = b1;
b1 = remainder;
}
Brain.Screen.printAt(5, 60, "GCD ( %d, %d ) = %d", a2, b2, a1);

a1 = a2 = 60;
b1 = b2 = 200;
while(remainder > 0){
remainder = a1 % b1;
a1 = b1;
b1 = remainder;
}
Brain.Screen.printAt(5, 60, "GCD ( %d, %d ) = %d", a2, b2, a1);
}
```

### 使用用户定义的函数：

```int getGCD(int a, int b){
int remainder = 1;
while(remainder>0){
remainder = a % b;
a = b;
b = remainder;
}
return a;
}

int main() {
vexcodeInit();
Brain.Screen.printAt(5, 60, "GCD ( %d, %d ) = %d",getGCD(20, 64));
Brain.Screen.printAt(5, 60, "GCD ( %d, %d ) = %d",getGCD(60, 100));
}
```

## 示例：平均一组数值

```loat doAverage(int n1, int n2, int n3){
float avg = (n1 + n2 + n3)/3;
return avg;
}

int main() {
int n1, n2, n3;
Brain.Screen.print("average(%d, %d, %d) = %d", 10, 20, 30);
doAverage(10, 20, 30);

n1=10; n2=20; n3=40;
Brain.Screen.print("average(%d, %d, %d) = %d", n1, n2, n3);
doAverage(n1, n2, n3);
}
```

## 示例：使一台机器人以可变编码器值前进

```void reportMotionValues(){
Brain.Screen.printAt(5,100, "%8.2lf%8.2lf%8.2f",
LeftMotor.position(rev),
LeftMotor.position(deg));
}

void goStraight(float totalEnc, float vel){
LeftMotor.resetPosition();
LeftMotor.setVelocity(50.0, percent);  LeftMotor.spinToPosition(totalEnc, deg, true);
return;
}

int main() {
int enc=1000; // >0: forward, <0: backward
vexcodeInit();

for(int i=0; i<10; i++){
enc *= -1;
goStraight(enc, 100);
Brain.Screen.printAt(5,60, "Done");
reportMotionValues();

//this delay is here only for you to view these actions.
//你不需要在这里设置一个延时。
wait(2000, msec);
}
}```

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