                                                                                                                                                                                                                                                                
Received-SPF: pass (google.com: domain of python-ideas-bounces+python-ideas-garchive-35620=googlegroups....@python.org designates 82.94.164.166 as permitted sender) client-ip=82.94.164.166;
MIME-Version: 1.0
In-Reply-To: <CAP7h-xZ4gET+7-m+j3d0L_z1LAnErgWzjFA9UcMdmNToH5U...@mail.gmail.com>
References: <CAOVPiMhnBezrw3gusD1QmW8MawV1HDCQHiTbd2Z0_T1TLDa...@mail.gmail.com>
	<506D94EE.30...@pearwood.info>
	<CAP7h-xZBg-MbWtmWFSQ4HmSPjCO_+Av_f-ip6hrH8WBSPJv...@mail.gmail.com>
	<CAPTjJmrRENuYXMOjPzobY1Hjkr+Vmqq04Z4_JOr6=DCdP4-...@mail.gmail.com>
	<CAP7h-xb4WvNuDGayqe60GRGmV4Nk-nzcN1d=HLahHw-hkG7...@mail.gmail.com>
	<CAP7+vJ+G-0WXZRTgr5Y=T+OdaMWmGzgk1--UH8=zoBGLsia...@mail.gmail.com>
	<CAP7h-xaV3RaA2EW4+vWuU=L=2JjhnKBGqhHPhgnmf4VbgGm...@mail.gmail.com>
	<CAP7+vJLt_WNzS75S25kMgPjFMiKz5DFCj5V69ZeyiWsYs5A...@mail.gmail.com>
	<50723BE5.3060...@nedbatchelder.com>
	<507243D2.8000...@btinternet.com>
	<CAP7+vJ+s+1o05t1WmgBxUEdLLdZX-vXMvZw8bMsDAzSv34i...@mail.gmail.com>
	<50736983.5030...@canterbury.ac.nz>
	<CAP7+vJJ4W3vVWT_EsVVxmp4HyWCB_pHZ8hSZRKKJraaEY6n...@mail.gmail.com>
	<CAHVvXxS+BASh_BQ=-p_RNtTCcwOcOYAFFnT9SCd+C5TTkm5...@mail.gmail.com>
	<CAP7+vJ+S_-FixjEhu-5t6fG8zZqAPdJFgk0cd5dzddkNtEm...@mail.gmail.com>
	<CAP7h-xZ4gET+7-m+j3d0L_z1LAnErgWzjFA9UcMdmNToH5U...@mail.gmail.com>
Date: Mon, 8 Oct 2012 20:38:13 -0700
Message-ID: <CANerV6mBTt3ALs_SPggbuMn-7X+FP9mCq5q9gshDWYb6MAW...@mail.gmail.com>
From: Case Van Horsen <cas...@gmail.com>
To: Alexander Belopolsky <alexander.belopol...@gmail.com>
Cc: python-id...@python.org
Subject: Re: [Python-ideas] checking for identity before comparing built-in
	objects
Precedence: list
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Errors-To: python-ideas-bounces+python-ideas-garchive-35620=googlegroups....@python.org
Sender: "Python-ideas"
	<python-ideas-bounces+python-ideas-garchive-35620=googlegroups....@python.org>

On Mon, Oct 8, 2012 at 6:37 PM, Alexander Belopolsky
<alexander.belopol...@gmail.com> wrote:
> On Mon, Oct 8, 2012 at 9:07 PM, Guido van Rossum <gu...@python.org> wrote:
>> If we want to do *anything* I think we should first introduce a
>> floating point context similar to the Decimal context. Then we can
>> talk.
>
> +float('inf')

I implemented a floating point context manager for gmpy2 and the MPFR
floating point library. By default, it enables a non-stop mode where
infinities and NaN are returned but you can also raise exceptions. You
can experiment with gmpy2: http://code.google.com/p/gmpy/

Some examples

>>> import gmpy2
>>> gmpy2.get_context()
context(precision=53, real_prec=Default, imag_prec=Default,
        round=RoundToNearest, real_round=Default, imag_round=Default,
        emax=1073741823, emin=-1073741823,
        subnormalize=False,
        trap_underflow=False, underflow=False,
        trap_overflow=False, overflow=False,
        trap_inexact=False, inexact=False,
        trap_invalid=False, invalid=False,
        trap_erange=False, erange=False,
        trap_divzero=False, divzero=False,
        trap_expbound=False,
        allow_complex=False)
>>> gmpy2.log(0)
mpfr('-inf')
>>> gmpy2.get_context()
context(precision=53, real_prec=Default, imag_prec=Default,
        round=RoundToNearest, real_round=Default, imag_round=Default,
        emax=1073741823, emin=-1073741823,
        subnormalize=False,
        trap_underflow=False, underflow=False,
        trap_overflow=False, overflow=False,
        trap_inexact=False, inexact=False,
        trap_invalid=False, invalid=False,
        trap_erange=False, erange=False,
        trap_divzero=False, divzero=True,
        trap_expbound=False,
        allow_complex=False)
>>> gmpy2.get_context().clear_flags()
>>> gmpy2.get_context().trap_divzero=True
>>> gmpy2.log(0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
gmpy2.DivisionByZeroError: 'mpfr' division by zero in log()
>>> gmpy2.set_context(gmpy2.context())
>>> gmpy2.nan()==gmpy2.nan()
False
>>> gmpy2.get_context()
context(precision=53, real_prec=Default, imag_prec=Default,
        round=RoundToNearest, real_round=Default, imag_round=Default,
        emax=1073741823, emin=-1073741823,
        subnormalize=False,
        trap_underflow=False, underflow=False,
        trap_overflow=False, overflow=False,
        trap_inexact=False, inexact=False,
        trap_invalid=False, invalid=False,
        trap_erange=False, erange=True,
        trap_divzero=False, divzero=False,
        trap_expbound=False,
        allow_complex=False)
>>> gmpy2.get_context().trap_erange=True
>>> gmpy2.nan()==gmpy2.nan()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
gmpy2.RangeError: comparison with NaN
>>>

Standard disclaimers:

* I'm the maintainer of gmpy2.

* Please use SVN or beta2 (when it is released) to avoid a couple of
embarrassing bugs. :(

> _______________________________________________
> Python-ideas mailing list
> Python-id...@python.org
> http://mail.python.org/mailman/listinfo/python-ideas
_______________________________________________
Python-ideas mailing list
Python-id...@python.org
http://mail.python.org/mailman/listinfo/python-ideas