\cut

Description 

Operator \cut breaks an existing edge into two parts with an intermediate vertex. A control is made to insure that the edge parameter really exists in the internal data but the system does not require that the second parameter (the vertex) geometrically belongs to the edge. Two new edges are created defined with each of the edge extremity and the vertex. The original edge is replaced in the internal structures by one of the new edges, the second one is created and inserted. Thus, the original edge does not exist anymore in the internal structures and can't be used by another operator. This cut operation is often associated with the hide operator (cf. § ) for instance after a valley fold when the top layer hide some existing graphical elements.
This operator should only appear in a step block.

Usage

  \cut([a, b], ab2); % delete [a,b] and created its two half segments

Formal structure

  \cut(EDGE, VERTEX);

Parameters

  EDGE
  Description    : Indicates the edge to cut. 
  Type           : Edge, couple of vertex identifiers
  Allowed values : Any couple of vertex identifiers already 
                   defined as an edge in a previous step.

  VERTEX
  Description    : Break vertex of the segment.
  Type           : Symbol, vertex identifier.
  Allowed values : Any vertex identifier previously defined.

Conditions

• EDGE should be already defined in the edges internal data.