grammar Expressive

  rule program
    statement* <Program>
  end

  rule statement
    whitespace* (list / atom) whitespace* <Statement>
  end

  rule atom
    (value / identifier)
  end

  rule list
    '(' statement+ ')' <List>
  end

  rule value
    (string / boolean / number)
  end

  rule word
    [a-zA-Z]+
  end

  rule string
    '"' ([^"\\] / "\\" . )* '"' <StringValue>
  end

  rule number
    ( float / integer )
  end

  rule integer
    [0-9]+ <IntegerValue>
  end

  rule float
    [0-9]+ ('.' [0-9]+) <FloatValue>
  end

  rule whitespace
    [\n\r\s\t]
  end

  rule parenthesis
    [\(\)\[\]]
  end

  rule boolean
    ('true' / 'false') <Boolean>
  end

  rule delimeter
    parenthesis / whitespace
  end

  rule identifier
    (!delimeter .)+ <Identifier>
  end

end