\symmetry

Description 

Operator \symmetry allows the creation of a new point as the symmetric of its first parameter through an axis (second parameter). The second parameter is an edge (represented as a couple of vertices with brackets ([ ]), but this syntaxic form does not means that the couple of vertices represents an existing edge in the edge internal data, it is just to make the operator more readable and not ambiguous. The only condition is that vertices are not equivalent.
This operator should only appear in a step block.

Figure: bc is built as the symmetrical point of da through edge [ab, cd]

Usage

  bc = \symmetry(da, [ab, cd]);

Formal structure

  \symmetry(VERTEX, EDGE);

Parameters

  VERTEX
  Description    : Vertex which has to be symmetrized.
  Type           : Symbol, vertex identifier.
  Allowed values : Any vertex identifier previously defined.
  EDGE
  Description    : Indicates the symmetry axis. 
  Type           : Edge, couple of vertex identifiers
  Allowed values : Any couple of vertex identifiers already 
                   defined in a previous step.

Return value

  RETURN_VERTEX
  Description    : New vertex symmetric of given VERTEX through EDGE.
  Type           : Symbol, vertex identifier.
  Allowed values : Any vertex identifier not already defined.

Conditions

• length of EDGE should not be null.