jython-dev

[Jython-dev] Float and imag literals

[Tim P. <ti...@zo...>]

Hi -- I'm about to check in a change to Python's float literal syntax:

http://sf.net/tracker/?func=detail&atid=305470&aid=455966&group_id=5470

Currently, CPython doesn't allow a float or imag literal to begin with a
string of digits that "looks like" an octal literal, except for the specific
prefix "0.".  Things like

   00.0
   0e3
   0100j
   09.5

are all rejected as SyntaxErrors.  After the patch, those are all accepted.

Will this create problems for Jython?  It required looking ahead in Python's
by-hand lexer (e.g.,

    090000000000000.

is a legit float literal after the patch, but take off the trailing point
and it's still a SyntaxError (an octal literal with the digit '9').

significant-leading-zeroes-are-insane-ly y'rs  - tim

Re: [Jython-dev] Float and imag literals

[<bc...@wo...>]

[Tim Peters]

>Hi -- I'm about to check in a change to Python's float literal syntax:
>
>http://sf.net/tracker/?func=detail&atid=305470&aid=455966&group_id=5470
>
>Currently, CPython doesn't allow a float or imag literal to begin with a
>string of digits that "looks like" an octal literal, except for the specific
>prefix "0.".  Things like
>
>   00.0
>   0e3
>   0100j
>   09.5
>
>are all rejected as SyntaxErrors.  After the patch, those are all accepted.
>
>Will this create problems for Jython?

No. Jython can handle some of these already:

Jython 2.1a3 on java1.3.0 (JIT: null)
Type "copyright", "credits" or "license" for more information.
>>> 00.0
0.0
>>> 0e3
0.0
>>> 0100j
Traceback (innermost last):
  (no code object) at line 0
  File "<console>", line 1
        0100j
            ^
SyntaxError: invalid syntax
>>> 09.5
9.5
>>>

The failing one is as easy to fix as it should be, when you have a
general purpose lexer at your disposal.

regards,
finn

RE: [Jython-dev] Float and imag literals

[Tim P. <ti...@ho...>]

[Finn Bock]
> No. Jython can handle some of these already:

Great!  Think of this as CPython following Jython's lead, then <wink>.

> ...
> The failing one is as easy to fix as it should be, when you have a
> general purpose lexer at your disposal.

Ya, I figured it would be.  It wasn't hard in CPython either, where we enjoy
the magical power of mountains of gotos <snort>.

more-than-one-way-to-lex-a-token-ly y'rs  - tim