Edges

Edge is the main element that uses vertices. It is used to draw graphical line in steps. It contains both extremity symbol names referencing to both vertices delimiting this edge. The Doodle notation of an edge used braces around the couple of vertices names:

  [a, b] % means the edge from 'a' to 'b'

Some geometrical operators (like \line_to_line or \rabbit_ear) return a couple of vertices. They use the edge notation for convenience and readability but they do not define an edge.

In an Origami point of view, edges are used to express paper limits (its borders), folds to apply (mountain or valley) and creases which result of application of folds. An edge is typed according to its Origami nature. For instance, a line used to draw a valley fold will be considered as a valley edge. Section explains how edge types are changed from step to step.

Edges can be modified by operators (such as \cut) but like vertices a defined edge cannot be physically removed from the internal structure. Even if an edge is hidden (using operator \hide) it remains in data structure. This way, it guarantees that at any moment it can be restored in steps (using operator \show).

Edges can always be accessed once they have been defined¹.