[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

Re-opening for further discussion.

-1 on Nick's suggestion to normalize hex output so that nearby floats 
have nearby reprs.  This unnecessarily complicates a simple, straight-
forward presentation.  In the paper referenced by Terry Reedy, 
normalized presentations were not used and I've never seen that done 
anywhere else.

IMO, the patch is fine as-is.

--
status: closed -> open
Added file: http://bugs.python.org/file10724/float6.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

Applied in r64438

--
status: open -> closed

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Mark Dickinson]

Mark Dickinson <[EMAIL PROTECTED]> added the comment:

> Mark, I added tests for Inf/Nan.  Will this work on all platforms?

I think the tests should work on all common to semicommon platforms, 
including on all the buildbots.  They won't work on non IEEE 754 platforms 
(float('nan') will throw an exception).  Then again, neither will all the 
Inf/NaN tests in test_math.py.  Sigh.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Changes by Raymond Hettinger <[EMAIL PROTECTED]>:


Removed file: http://bugs.python.org/file10674/float5.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

Mark, I added tests for Inf/Nan.  Will this work on all platforms?

Added file: http://bugs.python.org/file10675/float5.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Changes by Raymond Hettinger <[EMAIL PROTECTED]>:


Added file: http://bugs.python.org/file10674/float5.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

Hmm, I don't see a way to preserve -0.0 without varying from the 
standard format.

Attaching an updated patch for Amaury's comments.

Added file: http://bugs.python.org/file10673/float4.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Mark Dickinson]

Mark Dickinson <[EMAIL PROTECTED]> added the comment:

The patch looks good to me.

It's a bit unfortunate that -0.0 doesn't round-trip correctly (the sign 
of the zero gets lost):

>>> eval(bin(-0.0))
0.0

I don't know whether it's worth special-casing this;  the output would 
have to be in a different format:  '-0b0 * 2.0 ** 0' isn't good enough, 
since unary minus has higher precedence than multiplication.

--
nosy: +marketdickinson

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Amaury Forgeot d'Arc]

Amaury Forgeot d'Arc <[EMAIL PROTECTED]> added the comment:

I don't like this modification of a PyString object:

+   n = PyString_GET_SIZE(conv);
+   conv_str = PyString_AS_STRING(conv);
+   /* Remove the trailing 'L' if present */
+   if (n && conv_str[n-1] == 'L')
+   conv_str[n-1] = '\0';
+   result = PyString_FromFormat("%s * 2.0 ** %d", conv_str, exp);

The string may have other references (ex: all single-char strings are
shared) and it seems unwise to directly modify the memory.

Also, tests should check if negative numbers have the same
representation as their absolute value (with the sign). It is not
obvious from the implementation, which uses floor().

--
nosy: +amaury.forgeotdarc

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

The other reviewers asked for:
* same treatment for oct() and hex()
* platform independent exact representation of floats
* fixed-size exponential style output instead of tons of leading zeros
* output that round-trips through eval()
* use Py2.6 octal format in 2.6, and 3.0 format in 3.0

Attaching a patch with tests.

Added file: http://bugs.python.org/file10668/float3.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Changes by Raymond Hettinger <[EMAIL PROTECTED]>:


Added file: http://bugs.python.org/file10667/float2.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Changes by Raymond Hettinger <[EMAIL PROTECTED]>:


Added file: http://bugs.python.org/file10666/float.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Changes by Raymond Hettinger <[EMAIL PROTECTED]>:


Removed file: http://bugs.python.org/file10664/floatdisp.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

To address the ideas brought-up so far, here's a new version that can 
work with eval.  The same appoach extends to oct and hex as well:

def newbin(f):
"""
>>> newbin(3.125)
'0b11001 * 2.0 ** -3'
"""
n, d = f.as_integer_ratio()
s = '%s * 2.0 ** %d' % (bin(n), -math.log(d, 2.0))
return s

--
keywords: +patch
Added file: http://bugs.python.org/file10664/floatdisp.diff

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

Saving this for after the first beta goes out.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexandre Vassalotti]

Alexandre Vassalotti <[EMAIL PROTECTED]> added the comment:

Kind of a cool hack. I am not sure how useful it is though. Personally,
I find ``struct.pack('d', f)`` slightly more educative (more useful
too), but that is just me. 

And if you allow bin() to accept floats, will you make Python accept
binary float literals too?

--
nosy: +alexandre.vassalotti

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

No need to conquer the whole world.  Start with bin(1.1).  If requests 
pour-in for hex(1.1) or for a reverse routine, we can deal with those 
when we get them (in the context of their use cases).

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Terry J. Reedy]

Terry J. Reedy <[EMAIL PROTECTED]> added the comment:

> AFAICT, there is no good use case for showing floats in in hex

It is my impression that hexadecimal is more common than binary, in the
numerical analysis community, for exact representation of floats.

For example:
http://hal.archives-ouvertes.fr/docs/00/28/14/29/PDF/floating-point-article.pdf

"Hexadecimal floating-point representations are especially important
when values must be represented exactly, for reproducible results — for
instance, for testing “borderline cases” in algorithms."

Or course, without hex float literals or an equivalent function for
input, hex float output is not much use.

--
nosy: +tjreedy

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexander Belopolsky]

Alexander Belopolsky <[EMAIL PROTECTED]> added the comment:

On Fri, May 30, 2008 at 2:32 PM, Antoine Pitrou <[EMAIL PROTECTED]> wrote:

> then why not make it a method of float?

.. because you rarely want to make your functions accept 1.0, but
reject 1 and using f.bin() in your function will give it this
property.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexander Belopolsky]

Alexander Belopolsky <[EMAIL PROTECTED]> added the comment:

Another problem with bin() on floats is that it will be a one-way street
because as far as I know, there is no function to convert a binary
string back to a float.

My last thought on this issue is that it will be helpful to add
tobase(f, n) and frombase(s,n) functions to math module (and I withdraw
my suggestion of using %g-like notation due to the conflict between E
for exponent and E for 0xE).  On the other hand, there is no need to
mess up with builtin bin/oct/hex because with math.tobase float-capable
extensions will be trivially implementable.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

AFAICT, there is no good use case for showing floats in in hex or oct, 
so those should not chance.  Also, since bin() is new, no existing code 
is affected.  Thanks for the comments.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Antoine Pitrou]

Antoine Pitrou <[EMAIL PROTECTED]> added the comment:

> Better to just build-out bin() and be done with it.

Ok, someone has to take a decision anyway.

However, if you do that, it should be probably decided first what
happens for hex() and oct(). Do they still disallow floats (which is
semantically reasonable but makes things slightly inconsistent)? Or are
they also changed in order to return the same kind of things as bin()
does (which would probably give awful results)?

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

Raymond Hettinger <[EMAIL PROTECTED]> added the comment:

Better to just build-out bin() and be done with it.

FWIW, the action on ints and floats is similar to how str() handles 
numeric inputs:
  str(3)   --> '3'
  str(3.0) --> '3.0'
  bin(3)   --> '0b11'
  bin(3.0) --> '0b11.0'

--
assignee:  -> rhettinger

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Antoine Pitrou]

Antoine Pitrou <[EMAIL PROTECTED]> added the comment:

> What would you say to adding float-capable bin/oct/hex (+ maybe tobase)
> to the math module?

Why not indeed.
However, as I said, if the intent is float-specific (and it is, unless
there is another inexact numeric type which warrants a specific bin()
output), then why not make it a method of float?

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Antoine Pitrou]

Antoine Pitrou <[EMAIL PROTECTED]> added the comment:

> I read the proposal as
> producing the true mathematical radix 2 representation of a float
> rather than its 64-bit memory layout.

The term "layout" was probably badly chosen.
Still, the explicit motivation for producing that representation is that
it it supposed to educate people about the actual implementation of
floats. Other than that, a radix 2 representation is quite an obscure
(and almost never used) way of representing float objects. Binary
representation of integers in comparison is more widely understood and
more frequently used, which -- I suppose -- justifies the existence of a
builtin function to obtain it.

> I fail to see how the proposed bin(..) can produce '0b11.00100..' from
> a float that compares equal to 3.

Oops, you are right. bin(3.0) would produce '0b11.', which is indeed
more readable.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexander Belopolsky]

Alexander Belopolsky <[EMAIL PROTECTED]> added the comment:

What would you say to adding float-capable bin/oct/hex (+ maybe tobase)
to the math module?

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexander Belopolsky]

Alexander Belopolsky <[EMAIL PROTECTED]> added the comment:

On Fri, May 30, 2008 at 1:47 PM, Antoine Pitrou <[EMAIL PROTECTED]> wrote:
..
> 1. while taking the binary representation of an integer has a real
> meaning, taking the binary representation of a float only exposes an
> implementation detail, that is the internal layout of float numbers.
>
You may have misunderstood the proposal.  I read the proposal as
producing the true mathematical radix 2 representation of a float
rather than its 64-bit memory layout.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexander Belopolsky]

Alexander Belopolsky <[EMAIL PROTECTED]> added the comment:

On Fri, May 30, 2008 at 1:47 PM, Antoine Pitrou <[EMAIL PROTECTED]> wrote:
..
> 2. if two numbers (one integer and one float) are equal, it sounds
> expectable that calling a function on them will produce similar output
> (or fail). .. While getting something like
> '0b11.001001110110101010001000110110100011' while you were
> waiting for '0b11' is disturbing.

I fail to see how the proposed bin(..) can produce '0b11.00100..' from
a float that compares equal to 3.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Antoine Pitrou]

Antoine Pitrou <[EMAIL PROTECTED]> added the comment:

> I think you are mistaken.  Python always distinguished between floats
> and integers

Sorry, my bad.

> For example, if
> bin is used inside f()  only to  produce some log output,  but
> otherwise f() works on any number, promiscuous bin() will actually
> make an application using f() more robust.

First I'm not sure bizarre log output should be considered "more
robust". Second if you are outputting the bin() of an integer as part of
a log output, it probably means the integer should be understood as a
kind of bitfield, and then I don't see how accepting float values is
"more robust" (again). Anyway Python doesn't accept floats for bit-wise
operators (e.g. "1.0&128" raises TypeError).

I still find this proposal undesirable, for several reasons:

1. while taking the binary representation of an integer has a real
meaning, taking the binary representation of a float only exposes an
implementation detail, that is the internal layout of float numbers. 

2. if two numbers (one integer and one float) are equal, it sounds
expectable that calling a function on them will produce similar output
(or fail). Of course, this is not always the case, str(1) and str(1.0)
are different. But they are not wildly different and the difference is
still easily understood. While getting something like
'0b11.001001110110101010001000110110100011' while you were
waiting for '0b11' is disturbing.

3. I'm skeptical about the educational value. People who don't know
about the internal layout of float numbers won't very likely feel
enlightened by a string of 1s and 0s. Showing a bunch of bits does not
really explain a structure.

One related feature, though, would be to know whether a string
representation of a float is exact or not. 
If we allowed repr() to lose its round-trippability, this could be
implemented by making repr(0.5) return "0.5 (exact)" and repr(0.1)
return "0.10001 (inexact)".
Or this could be a dedicated method.


> While writing my previous comments I did not realize that '%x' %
> accepts floats:

And witness how it does something rather intuitive (convert the argument
to int) rather than show the internal layout of the float number in
hexadecimal form :-)

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexander Belopolsky]

Alexander Belopolsky <[EMAIL PROTECTED]> added the comment:

While writing my previous comments I did not realize that '%x' % accepts
floats:

>>> "%x" % 3.1415
'3'

Float support has been even improved somewhat since 2.5:

Python 2.5 (r25:51908, Nov 24 2006, 11:03:50) 
>>> '%x' % 1e10
Traceback (most recent call last):
  File "", line 1, in 
TypeError: int argument required


The new stile formatting, however does not allow floats with either :x
or :b formats:

>>> "{0:x}".format(1.)
Traceback (most recent call last):
  File "", line 1, in 
ValueError: Unknown conversion type x

>>> "{0:b}".format(1.)
Traceback (most recent call last):
  File "", line 1, in 
ValueError: Unknown conversion type b


I don't think anything needs to be done about it given that % formatting
is being deprecated while new style format is doing the right thing IMO.

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexander Belopolsky]

Alexander Belopolsky <[EMAIL PROTECTED]> added the comment:

On Fri, May 30, 2008 at 10:52 AM, Antoine Pitrou <[EMAIL PROTECTED]> wrote:
>
> Antoine Pitrou <[EMAIL PROTECTED]> added the comment:
>
> Well it's quite simple. Imagine you have a function f() which takes an
> integer parameter named x, and somewhere applies bin() to this parameters.

This is too abstract.  Depending on what f() is designed to do,
accepting floats may  or may not be the right thing.  For example, if
bin is used inside f()  only to  produce some log output,  but
otherwise f() works on any number, promiscuous bin() will actually
make an application using f() more robust.
>
>
> Right now, if you call f(1.0) instead of f(1), you will get a TypeError,
> which is easy to detect: you then fix the call to f(1), and bin()
> produces the expected result ('0b1').

There is no "right now".  Builtin bin is new in 2.6.
>
> ..
>
> There is a reason Python recently introduced a stronger distinction
> between ints and floats (for instance the __index__ method, which bin()
> seems to use currently), I don't see the logic behind trying to undo it.

I think you are mistaken.  Python always distinguished between floats
and integers

Traceback (most recent call last):
  File "", line 1, in ?
TypeError: list indices must be integers
>>> int.__index__
Traceback (most recent call last):
  File "", line 1, in ?
AttributeError: type object 'int' has no attribute '__index__'

__index__ was introduced in order to allow user-defined class
instances to be used as indices without affecting the way floats are
treated.
>
>
> And it's not like printing the bin() representation of a float has any
> actually use (besides education, but education can use its own tools
> rather than builtin functions).

That's exactly my point.  Builtin bin being new, I cannot comment on
its actual use, but I've only used hex() in interactive sessions as an
easy to type alternative to the finger-twisting "0x%x" % incantation.
(IMO, "{0:b}".format(..) is even worse.)  In the scripts, however, you
would rarely need to create a string representation of single  number.
 More often you will need to embed a number in a larger message and
thus you will use % or str.format instead of bin/hex/oct anyways.

BTW, google code search quickly revealed the following antipattern:

   log.msg("real checksum: %s"%hex(hdr[19]))

(twisted-Zope-3.2.2/twisted/words/protocols/toc.py)

Surely "real checksum: %x" % hdr[19] would be a better choice.  (The
0x prefix generated by hex is just noise in the log output.)

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Antoine Pitrou]

Antoine Pitrou <[EMAIL PROTECTED]> added the comment:

Well it's quite simple. Imagine you have a function f() which takes an
integer parameter named x, and somewhere applies bin() to this parameters.

Right now, if you call f(1.0) instead of f(1), you will get a TypeError,
which is easy to detect: you then fix the call to f(1), and bin()
produces the expected result ('0b1').

With Raymond's suggestion, if you call f(1.0) instead of f(1), no
exception will tell you your mistake, and bin() will produce a
completely bogus result compared to the expected one. If you notice the
bogus function output and find out that it contains a strange-looking
string (something like
'0b11.001001110110101010001000110110100011'), it is still
not obvious from it that the problem stems from passing a float instead
of an int. Especially if f() is a library function which you didn't
write yourself.

There is a reason Python recently introduced a stronger distinction
between ints and floats (for instance the __index__ method, which bin()
seems to use currently), I don't see the logic behind trying to undo it.

And it's not like printing the bin() representation of a float has any
actually use (besides education, but education can use its own tools
rather than builtin functions).

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Alexander Belopolsky]

Alexander Belopolsky <[EMAIL PROTECTED]> added the comment:

I like the idea in general.  It is way too common for people to be 
confused by decimal representation of floats, so an obvious mechanism to 
display the true value will be helpful.

I don't think a promiscuous bin() will lead to obscure bugs. Antoine 
will  have to give a specific example to convince me otherwise.  I can 
see, that extending :b format to floats may be a problem, but this is 
not being proposed.

As far as the proposed implementation goes, I don't like the fact that 
it always returns a fixed rather than floating point notation. (Try 
vis(1e100)).  I think it should behave somewhat like "%g" format.

If bin() is extended to floats, it may become confusing that hex() and 
oct() are not similarly extended.

--
nosy: +belopolsky

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Antoine Pitrou]

Antoine Pitrou <[EMAIL PROTECTED]> added the comment:

Or, if you want to educate people at all cost, the TypeError raised by
bin() when trying it on a float object could include in its message the
binary representation of the float object "for edification". :-)

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Antoine Pitrou]

Antoine Pitrou <[EMAIL PROTECTED]> added the comment:

I'm not sure about the educational value of letting obscure bugs
creeping in when someone passes a float where an int is expected :-)
Your vis() function looks appropriate for the task of educating people,
why should its behaviour be folded into bin()?

--
nosy: +pitrou

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue3008] Let bin() show floats

[Raymond Hettinger]

New submission from Raymond Hettinger <[EMAIL PROTECTED]>:

Let bin() show floating point values.  This would contribute quite a 
bit to people's understanding of floating point arithmetic.  It has a 
nice education value and it makes it easier to diagnose floating point 
mysteries.

def vis(f):
""" Show binary representation of a floating point number:

>>> vis(math.pi)
'0b11.001001110110101010001000110110100011'
>>> vis(-0.375)
'-0b0.011'
"""
f, sign = (f, '') if f >= 0 else (-f, '-')
n, d = f.as_integer_ratio() if isinstance(f, float) else (f, 1)
n, d = map(lambda x: bin(x)[2:], (n, d))
n = n.rjust(len(d), '0')
s = list(n)
s.insert(len(n) - len(d) + 1, '.')
return sign + '0b' + ''.join(s)

--
components: Interpreter Core
messages: 67525
nosy: rhettinger
severity: normal
status: open
title: Let bin() show floats
type: feature request
versions: Python 2.6, Python 3.0

___
Python tracker <[EMAIL PROTECTED]>

___
___
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com