\debug_line

Description 

\debug_line is only used for debugging diagram during its elaboration. It should be used inside of a step block to draw additional information for the current step. The system displays visible edge name. Edge name is made by the name of its extremities and this name is shown at the center of the edge. So if an edge doesn't appear the reason is that it is hidden.

This operator is useful to locate edges after application of operators that alter internal vertices coordinates as \turn_over_vertical (cf. §) for instance.

This operator has three syntaxes. The shorter (without parameter) is a quick way to have a global view of edges. The second and third ones can be seen as query operators since they reply to questions such as ``Where are located edges containing point...?'' The second syntax takes in argument a vertices list. The result of this form is to draw on the step each edge name which contains one of the given vertices. The third form replies to the question ``Where is located the edge...?''.
This operator should only appear within a step block.

Usage

  \debug_line;          % Display the name of all vertices
  \debug_line(a, cd1);  % Show me all edges containing a and cd1
  \debug_line([a, b]);  % Where is edge [a, b] ?

Formal structure

  \debug_line;
  \debug_line(VERTICES_LIST);
  \debug_line(EDGE);

Parameters

  VERTICES_LIST  : Any searched vertices.
  Type           : List of vertex symbols.
  Allowed values : Any sequence of vertex identifiers already 
                   defined in previous steps.
  EDGE
  Description    : Indicates the edge to locate.
  Type           : Edge, couple of vertex identifiers.
  Allowed values : Any couple of vertex identifiers already 
                   defined in a previous step.