Vladimir Yanakiev - 5 months ago 53

C++ Question

I have class Line, which represent 2 dimensional line. It has function for checking if 2d point lie on this line.

`class Line`

{

private:

float a,b,c: //line coefficients

public:

bool checkPointOnLine();

.....

}

now I have to check find point of intersectionof 2 lines. I'm wondering if it is better to put new member function in class Line like

`class Line`

{

private:

float a,b,c: //line coefficients

public:

bool checkPointOnLine();

Point getIntersectionPoint(const Line& line);

.....

}

or to use non member function

`Point getIntersectionPoint(const Line& l1,const Line& l2);`

Answer

Although to a large measure this is a matter of preference, a static or non-member function approach is slightly more preferable because of symmetry.

When two calls

```
a.someFunction(b)
```

and

```
b.someFunction(a)
```

always return the same result, a symmetric function

```
someFunction(a, b)
```

is more intuitive.

Note that since an intersection may not exist (for parallel lines) or have an infinite number of points (for two identical lines) returning a `Point`

is not ideal. You would be better off returning a pair of `Point`

and some indicator of its validity, for example

```
enum LineIntersectionKind {
Valid
, Empty
, Infinite
};
pair<Point,LineIntersectionKind> getIntersectionPoint(const Line& l1,const Line& l2);
```