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Advanced Programming Techniques in D

Struct and Class Templates

Explore how to transform structs and classes into templates in D programming to achieve scalable and type-independent code. Understand how to define template parameters, adapt existing code for template use, and specialize functions for template instantiations, enabling precise and reusable structures like Point for different data types.

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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 =
...