Components

This framework offers component-based development. Components exist at various levels of development and can be combined into larger components. Components can also contain sub-components. A component defines a composable entity whose role can vary from a driver to a functional component.

A component contains two entities: an interface, which is shared between all components of the same type, and an implementation-specific configuration.

For example, we will define a square whose interface is a generic shape.

interface Shape
{
    using Area = Integer [min(0)];
    method surface() -> Area;
}

component Square : Shape
{
config:
    width = Integer;
}

A square is defined by its width. Such a component is instantiated from a composable scope:

composition
{
    square = Square(width = 12);
}

This component exposes the Shape interface.

Sub-components

Components can be made from other components. The syntax is similar to a top level component, except that everything takes part in the component definition.

component ComplexShape : Shape
{
config:
    width1 = Integer;
    width2 = Integer;

composition:
    square1 = Square(width = width1);
    square2 = Square(width = width2);
}

The C++ implementation of the complex component could be something like:

Area ComplexShape::surface()
{
    return square1.surface() + square2.surface();
}

Sub-components help with encapsulation, reducing complexity and improving composability and reusability. For example, imagine a complex sub-system:

component RobotLeg : Kinematics
{
config:
    actuator1 = Actuator;
    actuator2 = Actuator;
    actuator3 = Actuator;
    logger = Logger;

composition:
    connect(this.actuator1.error, logger);
    connect(this.actuator2.error, logger);
    connect(this.actuator3.error, logger);
}