anchor.diff:    
   Terminals
     eol '(' ')' '[' ']' '{' '}'
  -  float integer identifier atom true false nil erl
  +  float integer atom true false nil 
  +  identifier punctuated_identifier erl
     '+' '-' '*' '/' '%' '**' ',' '.' '=' '=>'
     '+=' '-=' '*=' '/=' '**='
     .
  
positive.code:   unary_expr
    call_expr
    max_expr
    rebind_op
    add_op
    mult_op
  
negative.code:   block     = #nil{line=?line('$2')}
  }.
  
  call -> call_expr '.' function_identifier '(' exprs ')' :
  #remote_call{
    line      = ?line('$2'),
    receiver  = '$1',
  