we need a way for the lexer file to contain multi-line expressions,
or at least a reliable way to add comments, for now keep a copy here

(?E{t_def.FloatLiteral}
  (
    (?E{t_def.FloatLiteral.Integer}
      (?E{t_def.Text.Char}[0-9])
      (\ *(?E{t_def.Text.Char}[0-9]))*
    )
    (?E{t_def.FloatLiteral.Fraction}
      ""
    )
    |
    (?E{t_def.FloatLiteral.Integer}
      ((?E{t_def.Text.Char}[0-9])\ *)*
    )
    (?E{t_def.FloatLiteral.Fraction}
      \.
      (\ *(?E{t_def.Text.Char}[0-9]))*
    )
  )
  (?E{t_def.FloatLiteral.Exponent}
    \ *E
    (?E{t_def.FloatLiteral.Sign}
      (\ *(?E{t_def.Text.Char}[+-]))?
    )
    \ *
    (?E{t_def.FloatLiteral.Integer}
      (?E{t_def.Text.Char}[0-9])
      (\ *(?E{t_def.Text.Char}[0-9]))*
    )
  )?
)