Name of variable 

  - cannot be longer than 32 characters length,
  - can cannot start with a digit,
  - can have any characters except: ASCII characters 32, 9, 13, 10,
  - dollar character "$" make name variable which explained below.


Variables can be used in operations and string-expressions.

All variables have type "string". 
    
    In other words, values of variables are strings of ASCII characters.
    However, if used in arithmetical operations, they
    interpreted as long integers (, or in case of division "\", as double rationals )
    If value was not assigned to variable, variable has initial value empty "".
    If empty variable used in arithmetical operations, this variable is assigned value 0.


Variable names allowed:
  example: if variable $moo has value foo, and
              variable $boo has value "_own_$moo"
           then
             $moo      - will refer to name "foo",
             my$moo    - will refer to name "myfoo",
             my$boo    - will refer to name "my_own_foo"


Variables can be included in string-expressions with format
   $<variable_name><limitor>
       <limitor> is one of  " ", CR, LF, TAB, double qoutes ", or simply end of string;
         " "              - is sacrificed (removed when substituting variable);
         other limitors   - are not;


There are 25 intrinsic (reserved variable) names:
=================================================
with their name, initial values, and description:

  token                ""     current token
  type                 ""     current event type
  indent                      INDENT  
                              (after assigning v=indent, INDENT becomes empty)
                              explained in indent_help.txt.
  in                   ""     SourceText;
                              assignment ..=in."text" automatically assigns pos = 1;
  out                  ""     ResultText
  pos                  1      current position in SourceText during execution;		
  p_round                     round number useful for projects which 
                                     parse source multiple times
  @                           NestVariable; Assosiated with each global nest position.
  #                           current position in the global nest (=global nest length); read-only;
                              value is a number;
  @state                      current state; value is a string;                    
  @nest                       current nest;  value is a string;


  p_file_for_GUI              name of currently processed file to be
                              displayed in GUI box; 
  p_source                    source project
  p_version                   S2S version

This variables explained in file:
project_and_schema_structure_help.txt/"File Tree Structure"

  p_basic                     source file basic name
  p_extension                 source file extension
  p_rbasic                    result file basic name
  p_rextension                result file extension
  p_local_path                relative path to parent folder of currently processed file
                                     "relative" means relative to parent of source 
  p_umbrella     
  p_shield       
  p_parent       
  p_rparent      
  p_processed_files  
  p_file             
  p_rfile            


Some file-system variables described in:   project_and_schema_structure_help.
Additional information is in:              arithmetical_commands_and_assigments_help.txt