anchor.diff:  max_expr -> number       : '$1'.
   max_expr -> list         : '$1'.
   max_expr -> tuple        : '$1'.
  +max_expr -> map          : '$1'.
   max_expr -> identifier   : '$1'.
   max_expr -> atom         : '$1'.
   max_expr -> '(' expr ')' : '$2'.
  
positive.code: tuple -> '(' expr ',' ')' : #tuple{line=line('$1'), elements=['$2']}.
  tuple -> '(' expr ',' exprs ')': #tuple{line=line('$1'), elements=['$2'|'$4']}.
  
  Erlang code.
  
  -export([string/1]).
  
negative.code:   unary_op
    number
    list
    tail
    tuple
    map
    map_entries
    .
    
  Terminals
    eol '(' ')' '[' ']' '{' '}'
    float integer identifier atom
    '+' '-' '*' '/' '%' '**' ',' '=' '=>'
    .
  
  Rootsymbol grammar.
  