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Advanced Programming Techniques in D

Struct and Class Templates

You will learn about structs and class templates in this lesson.

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The Point struct may be seen as having a limitation. Because its two members are defined specifically as int, it cannot represent fractional coordinate values. This limitation can be removed if the Point struct is defined as a template.

Let’s first add a member function that returns the distance to another Point object:

D
import std.math; 



// ...



struct Point {

    int x;

    int y;

    int distanceTo(Point that) const { 

        immutable real xDistance = x - that.x; 

        immutable real yDistance = y - that.y;

        immutable distance = sqrt((xDistance * xDistance) + 

                                  (yDistance * yDistance));

        return cast(int)distance;

    }

}



void main() {}

That definition of Point is suitable when the required precision is relatively low: It can calculate the distance between two points at kilometer precision, e.g., between the center and branch offices of an organization:

auto center = getResponse!Point("Where is the center?"); 
auto branch =
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