\label

Description 

This operator allows user to set a virtual mark on steps to further use this mark as a reference of those steps. \label uses a symbol to alias the step which it belongs to. Therefore, this symbol can be used as the index of this step using the dual operator \ref (see cf. §). The parameter is not a string but a symbol, it is seen as a label identifier which has nothing in common with vertex identifier. As the label and vertex identifiers belong to two different symbol tables, user can use a same identifier for both a vertex and a label. Nevertheless, such usage can be confusing.

Such labels can be used also in the operator \repeat_arrow which can takes two labels to designate the begin and the end step of the repeat (see cf. § for more information on this operator).
This operator should only appear within a step block.

Usage

\step {
  ...
  \label(beginStep); % we are in the begin step, so
  ...                % beginStep is equivalent to 1
}

Formal structure

  \label(SYMBOL);

Parameters

  SYMBOL
  Description    : Indicates the label symbol. 
  Type           : Symbol, label identifier (same as vertex identifier).
  Allowed values : Any label identifier not previously defined.