main.cpp: In member function 'double Line::GetDistance()': main.cpp:56:5: error: expected initializer before 'distance' distance= sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));

这个错误是因为在使用变量 `distance` 之前没有进行初始化。你需要在函数的开头给 `distance` 赋一个初始值，例如：

double Line::GetDistance()
{
    double distance = 0.0; // 给 distance 赋初值
    distance = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
    return distance;
}

这样就可以解决这个编译错误了。

相关问题

FormInfo class FormInfo <<partial>> [ +Formlnfo0- button1 Click(sender:obiect, e:EventArgs) : void+ SetText(run:double, walk:double) : void Form <-- FormInfo Common class Common!+ static) map left lon : double +{static) map top lat : double +{static map right lon : double +{static' map bottom lat : double class Station { +longitute :double <<get>> <<set> >+latitude :double <<get> > <<set>> + staionname :string <<get>> <<set>> + stationlD :int <<get> > <<set>> + address :string <<get>> <<set> > + totalDocks :int <<get> > <<set> > + docksln :int <<get> > < <set> > + status : string <<get> > < <set> > Station-->"screenPoint"Point Form1 class Form1 <<partial>> !-imgH:int- imgW :int isStartSite : bool isEndSite : boolI startIndex :int- endIndex :int - isPlanRoute : bool = false- m distance : double = 0 +Form10 Form1 Shown(sender:obiect,e:EventArgs) : void panelRight SizeChanged(sender:obiect,e:EventArgs): void panelButtom SizeChanged(sender:object, e:EventArgs) : voidForm1 Paint(sender:object, e:PaintEventArgs) : void buttonlmport Click(sender:object, e:EventArgs) : void Import(fileName:string): void GPSToScreen(lon:double.lat:double): PointGetTitude(point:Point): doubel listStations SelectedlndexChanged(sender:obiect, e:EventArgs) : void panel2 Paint(sender:object, e:PaintEventArgs) : voidcheckAll Click(sender:obiect, e:EventArgs) : void comboBox1 SelectedndexChanged(sender:obiect.e:EventAras): voioDrawReqularPoly(x:float, y:float, radius:double, sideCount:int) : PointF panelMouse Paint(sender:obiect,e:PaintEventArgs) : void panelMouse MouseMove(sender:object, e:MouseEventArgs) : voidpanelMouse MouseClick(sender:object, e:MouseEventArgs) : voidbutton1 Click(sender:object, e:EventArgs) : void setRoute0:void - setWalkRoute() : void - comboBox1 TextChanged(sender:object, e:EventArgs) : void class"List1"<T>{ MapHelper class MapHelper!<<const>> EarthRadius : double = 6378.137Istatic' Rad(d:double) : double +Istatic' GetDistance(firstLatitude:double.firstLongitude:double, secondLatitude:doublesecondLongitude:double): double+Istatic1 GetPointDistance(firstPoint:string,secondPoint:string): double Form <-- Form1 Form1-->"allstation<Station>""List1"Form1-->"startPoint"Point Form1-->"endPoint"Point Form1-->"startList<PointFI>""List1" "routeList<PointFIl>""List1Form1-->Form1-->"endList<PointFIl>""List1"Form1-->"m formlnfo"FormInfo画类图

根据提供的信息，可以绘制以下类图：

+-----------------------------------+
|            FormInfo               |
+-----------------------------------+
| +Formlnfo0- button1 Click(...)    |
| +SetText(run:double, walk:double) |
+-----------------------------------+

+-----------------------------+
|            Form             |
+-----------------------------+
| <-- FormInfo                |
+-----------------------------+

+-----------------------------+
|           Common            |
+-----------------------------+
| +{static} map left lon      |
| +{static} map top lat       |
| +{static} map right lon     |
| +{static} map bottom lat    |
+-----------------------------+

+-----------------------------+
|          Station            |
+-----------------------------+
| +longitude : double         |
| +latitude : double          |
| +stationname : string       |
| +stationlD : int            |
| +address : string           |
| +totalDocks : int           |
| +docksln : int              |
| +status : string            |
| --> "screenPoint" Point     |
+-----------------------------+

+-----------------------------+
|          Form1              |
+-----------------------------+
| <-- FormInfo                |
| - imgH: int                 |
| - imgW: int                 |
| - isStartSite: bool         |
| - isEndSite: bool           |
| - startIndex: int           |
| - endIndex: int             |
| - isPlanRoute: bool = false |
| - m distance: double = 0    |
| +Form10                     |
| +Form1 Shown(...)           |
| +panelRight SizeChanged(...)|
| +panelButtom SizeChanged(...)|
| +Form1 Paint(...)           |
| +buttonlmport Click(...)    |
| +Import(fileName:string)    |
| +GPSToScreen(lon:double, lat:double): Point |
| +GetTitude(point:Point): double |
| +listStations SelectedlndexChanged(...) |
| +panel2 Paint(...)          |
| +checkAll Click(...)        |
| +comboBox1 SelectedndexChanged(...) |
| +DrawReqularPoly(...)       |
| +panelMouse Paint(...)      |
| +panelMouse MouseMove(...)  |
| +panelMouse MouseClick(...) |
| +button1 Click(...)         |
| - setRoute0:void            |
| - setWalkRoute() : void     |
| - comboBox1 TextChanged(...)|
+-----------------------------+

+-----------------------------+
|          List1<T>           |
+-----------------------------+

+-----------------------------+
|        MapHelper             |
+-----------------------------+
| <<const>> EarthRadius: double = 6378.137 |
| +static Rad(d: double): double         |
| +static GetDistance(firstLatitude: double, firstLongitude: double, secondLatitude: double, secondLongitude: double): double |
| +static GetPointDistance(firstPoint: string, secondPoint: string): double |
+-----------------------------+

请注意，这只是根据提供的信息绘制的大致类图，可能会有一些缺失或错误。

1．面向对象的应用：设计并测试一个表示一点的 MyPoint 类。 具体要求： 1) 该类包括以下私有属性： i. x:点的横坐标 ii. y:点的纵坐标 2) 包括如下方法： i. __init__()(self,x,y):构造方法，创建对象的同时为属性 x,y 赋初值； ii. getX()：获得点的横坐标。 iii. getY()：获得点的纵坐标。 iv. getDistance(self,p)：返回当前点与点 p 之间的距离。 两点间距离公式： 3) 完成类的实例化，并计算点 P1（0，0）到点 P2（5，5）的距离，并打印出来

可以参考以下代码实现：

import math

class MyPoint:
    def __init__(self, x, y):
        self.x = x
        self.y = y
    
    def getX(self):
        return self.x
    
    def getY(self):
        return self.y
    
    def getDistance(self, p):
        distance = math.sqrt((self.x - p.getX()) ** 2 + (self.y - p.getY()) ** 2)
        return distance

p1 = MyPoint(0, 0)
p2 = MyPoint(5, 5)
distance = p1.getDistance(p2)
print("P1到P2的距离为：", distance)

输出结果为：

P1到P2的距离为： 7.0710678118654755