Hello,
There is a programming technique that I use occasionally in my own programming, and I'm wondering whether anyone knows the name, and whether there are any articles/essays written about its use.
Here is the set up:
I have a typed tree datastructure that represents my source-of-truth. There is care put into ensuring this datastructure is clean, and to avoid redundancy. Here is an example of a basic tree of circles, with some made-up notation.
class CircleWorld {
List<Shape> shapes;
List<Style> styles;
}
class Circle <: Shape {
ID id;
double x;
double y;
double radius;
ID style;
}
class UnionedShapes <: Shape {
List<Shape> shapes;
}
class TranslatedShape <: Shape {
Shape shape;
double dx;
double dy;
}
class Style {
ID id;
Color color;
boolean is_opaque;
}
Here are some observations about this raw datastructure:
-
To compute the absolute coordinates of a Circle, you need the entire chain of TranslatedShape that lead up to it.
-
To look up the color of a Circle, you need to retrieve the corresponding Style object given its id.
-
Given only a Circle object, you can't retrieve either its absolute coordinates or its color, you also need the CircleWorld object.
For an object-oriented programmer, it is normal to expect to be able to query all sorts of useful information about an object given just its handle. For example:
-
Given a Circle, you can directly look up its absolute coordinates and color.
-
Given a Style, you can directly look up all the circles with this style.
-
etc.
So I can use a simple preprocessing algorithm to convert a CircleWorld datastructure into a ViewOfCircleWorld datastructure, where I can easily query for information given just an object handle. The two main advantages that I gain from this technique is that:
-
I expose an API that is easy and familiar to object-oriented programmers.
-
All the small "algorithms" for interpreting the raw datastructure, e.g. for looking up the color of a circle, are consolidated into one central place, so there's less need for each individual programmer to understand the structure of the raw datastructure.
So, here's my questions:
-
Does this technique have a name?
-
Does anyone else encounter similar problems, and have other ways of approaching it?
Thanks very much!
