Basic 2D Geometry Definition

Points, lines and arcs (up to full circles) are called basic geometry and can be defined by the user in a various number of ways. Such an alternative is referred to as a point mode, line mode or arc mode respectively. The different point, line and arc modes are described below. In almost every situation where the user is requested to supply one of these basic entities, the user has the opportunity to redefine the system-proposed mode. The system-proposed mode depends on the circumstances and the kind of geometry to supply. Since some of the point definitions require a line or an arc and some of the line and arc definitions, in turn, require a point, the point definition is recursive. The same applies when defining lines and arcs.

This fact enables the user to define geometry in a true recursive fashion, without having to explicitly create construction geometry in advance. The recursive depth is unlimited. The geometry definition facilities will throughout this manual be referred to as "GET POINT", "GET LINE", and "GET ARC", respectively, and should be interpreted as a general way of defining basic geometry. Thus, when user-supplied basic geometry is requested and the basic geometry definition is supported, the current invoked application function will just refer to this facility without considering the way it was defined. In some situations, the system requests an arbitrary segment which may be either a line or an arc. The general way of defining segments is called "GET SEGMENT", and is merely a combination of "GET LINE" and "GET ARC".