anchor.diff:  
   [source, ruby]
   ----
  -my_tokens_table = {}
  +my_tokens_table = AsciiMath::SymbolTableBuilder.new
  +AsciiMath::Parser.add_default_parser_symbols(my_tokens_table)
  +my_tokens_table.add('mysymbol', :mysymbol, :symbol)
   
  -AsciiMath::Tokenizer::DEFAULT_PARSE_SYMBOL_TABLE.each do |key|
  -  my_tokens_table[key] = AsciiMath::Tokenizer::DEFAULT_PARSE_SYMBOL_TABLE[key]
  -end
  -
  -my_tokens_table['mysymbol'] = {:value => :mysymbol, :type => :symbol}
  -
  -AsciiMath::parse("a + mycustomsymbol + b", my_tokens_table)
  +AsciiMath::parse("a + mycustomsymbol + b", my_tokens_table.build)
   ----
   
   Furthermore, the behaviour of the tokenizer be customized by altering the value 
  
positive.code: 
  [source, ruby]
  ----
  my_rendering_table = {}
  
  AsciiMath::MarkupBuilder::DEFAULT_DISPLAY_SYMBOL_TABLE.each do |key|
    my_tokens_table[key] = AsciiMath::Tokenizer::DEFAULT_PARSE_SYMBOL_TABLE[key]
  end
  
  my_rendering_table['alpha'] = {:value => '\u03b2', :type => :identifier}
  
  # Now "alpha + beta" is equivalent to "beta + beta"
  AsciiMath::parse("alpha + beta").to_mathml(my_rendering_table)
  ----
  
  ## Notes on the HTML Output
  
negative.code: 
  [source, ruby]
  ----
  my_tokens_table = AsciiMath::SymbolTableBuilder.new
  AsciiMath::Parser.add_default_parser_symbols(my_tokens_table)
  my_tokens_table.add('alpha', :beta, :symbol)
  
  # Now "alpha + beta" is equivalent to "beta + beta"
  AsciiMath::parse("alpha + beta", my_tokens_table.build)
  ----
  
  The same behaviour applies to each individual render (`MathMLBuilder`, 
  