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Groups > comp.lang.python > #71368
| From | Mark H Harris <harrismh777@gmail.com> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Fortran (Was: The "does Python have variables?" debate) |
| Date | 2014-05-11 23:26 -0500 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <lkpiic$a27$1@speranza.aioe.org> (permalink) |
| References | (12 earlier) <lkn4mh$4d5$1@speranza.aioe.org> <87mweotfe5.fsf@dpt-info.u-strasbg.fr> <lkoh14$rpq$1@speranza.aioe.org> <mailman.9906.1399865515.18130.python-list@python.org> <lkphk8$88v$1@speranza.aioe.org> |
On 5/11/14 11:10 PM, Mark H Harris wrote:
> On 5/11/14 10:10 PM, Dave Angel wrote:
>> On 05/11/2014 02:54 PM, Mark H Harris wrote:
>>
>>>
>>> >julia> sin(BigFloat(π/4))
>>> > 7.0710678118654750275194295621751674626154323953749278952436611913748
>>> > 20215180412e-01 with 256 bits of precision
>>>
>>
>> That answer doesn't seem to come anywhere near 256 bits of precision.
>>
>> Using Python 3.2,
>>
>> >>>
>> x=70710678118654750275194295621751674626154323953749278952436611913748
>> >>> x*x
>> 4999999999999999693838300213161705693483516931249926767981110058185818806614907837502621065882204197129973479350206261627418690991407504
>>
>>
>>
>> Not that this is surprising, but it does make a terrible ad for how
>> great Julia is.
>>
>
> Dave, you get the golden egg! I expected D'Aprano to catch it first!
>
> Yes, BigFloat does the same dumb thing Python's Decimal does. π/4 is
> not a BigFloat, and BigFloat simply makes the 16 digit float into a 256
> bit float, the sin of which will only be 16 digits accurate (more or less).
>
> It has nothing to do with the language (Python vs. Julia) it has to do
> with the way the BigFloat is formed. So let's fix it by forming the π
> constant as a BigFloat constant:
>
> >julia> n = BigFloat(1)
> >1e+00 with 256 bits of precision
>
> >julia> π = atan(n/5)*16 - atan(n/239)*4
> >3.141592653589793238462643383279502884197169399375105820974944592307816406286198e+00 >with 256 bits of precision
>
> >julia> S = sin(π/4)
> >7.07106781186547524400844362104849039284835937688474036588339868995366239231051e-01 >with 256 bits of precision
>
> >julia> S * S
> >4.999999999999999999999999999999999999999999999999999999999999999999999999999957e-01 >with 256 bits of precision
Having said that, the accuracy was not my point; in the first place. My
point is that the sin() function is built-in, takes standard floats (32
bit, 64 bit, 128 bit) and BigFloats of arbitrary precision (and does
something meaningful with it). Let's take a look at Python Deciaml:
>>> =================== RESTART ===============
>>> from decimal import * (first I have to import)
>>> from math import * (than I have to import again)
>>> π
Traceback (most recent call last):
File "<pyshell#13>", line 1, in <module>
π
NameError: name 'π' is not defined (whoops, don't know π )
>>> π=4*atan(1) (let's create it)
>>> sin(Decimal(π/4))
0.7071067811865475 (whoops sin doesn't do Decimals)
>>> from pdeclib import sin (let's get a sin that does do Decimals)
>>> sin(Decimal(π/4))
Decimal('0.707106781186547502751942956217516746261543')
>>> S=sin(Decimal(π/4)) (Whoops has the same problem as BigFloat)
>>> S**2
Decimal('0.499999999999999969383830021316170569348351')
>>>
Now let's fix it:
>>>
>>> from pdeclib import d
>>> n=d(1)
>>> from pdeclib import *
>>> n=d(1)
>>> π=atan(n/5)*16 - atan(n/239)*4
>>> S=sin(π/4)
>>> S**2
> Decimal('0.500000000000000000000000000000000000000000')
>>>
Also not bad, but slower. ;-)
marcus
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Re: The “does Python have variables?” debate Ned Batchelder <ned@nedbatchelder.com> - 2014-05-06 21:19 -0400
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-07 09:18 +0300
Re: The “does Python have variables?” debate Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-05-07 09:51 +0100
Re: The “does Python have variables?” debate Ethan Furman <ethan@stoneleaf.us> - 2014-05-07 06:00 -0700
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-07 17:17 +0300
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-08 00:30 +1000
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-08 00:14 +1000
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-07 17:20 +0300
Re: The “does Python have variables?” debate Jerry Hill <malaclypse2@gmail.com> - 2014-05-07 11:48 -0400
Re: The “does Python have variables?” debate Mark H Harris <harrismh777@gmail.com> - 2014-05-07 14:31 -0500
Re: The “does Python have variables?” debate Ben Finney <ben@benfinney.id.au> - 2014-05-08 05:57 +1000
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 00:15 +0300
Re: The “does Python have variables?” debate Mark H Harris <harrismh777@gmail.com> - 2014-05-07 16:35 -0500
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 01:27 +0000
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-08 12:09 +1000
Re: The “does Python have variables?” debate Steven D'Aprano <steve@pearwood.info> - 2014-05-08 03:41 +0000
Re: The “does Python have variables?” debate Dan Sommers <dan@tombstonezero.net> - 2014-05-08 03:43 +0000
Re: The “does Python have variables?” debate Mark H Harris <harrismh777@gmail.com> - 2014-05-09 17:34 -0500
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 01:11 +0000
Re: The “does Python have variables?” debate Larry Hudson <orgnut@yahoo.com> - 2014-05-10 00:46 -0700
Re: The “does Python have variables?” debate Ben Finney <ben@benfinney.id.au> - 2014-05-08 10:35 +1000
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 01:32 +0000
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 09:19 +0300
Re: The “does Python have variables?” debate Ben Finney <ben@benfinney.id.au> - 2014-05-08 16:40 +1000
Re: The "does Python have variables?" debate Rustom Mody <rustompmody@gmail.com> - 2014-05-07 23:50 -0700
Re: The "does Python have variables?" debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 10:03 +0300
Re: The “does Python have variables?” debate Ned Batchelder <ned@nedbatchelder.com> - 2014-05-07 21:33 -0400
Re: The “does Python have variables?” debate Johannes Schneider <johannes.schneider@galileo-press.de> - 2014-05-08 09:26 +0200
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-09 00:54 +0000
Re: The “does Python have variables?” debate Joseph Martinot-Lagarde <joseph.martinot-lagarde@m4x.org> - 2014-05-08 10:07 +0200
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-08 18:14 +1000
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 13:22 +0000
Re: The “does Python have variables?” debate Ben Finney <ben@benfinney.id.au> - 2014-05-08 18:34 +1000
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 12:43 +0300
Re: The “does Python have variables?” debate Ben Finney <ben@benfinney.id.au> - 2014-05-08 21:14 +1000
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 15:01 +0300
Re: The “does Python have variables?” debate Ben Finney <ben@benfinney.id.au> - 2014-05-09 05:14 +1000
Re: The “does Python have variables?” debate Ethan Furman <ethan@stoneleaf.us> - 2014-05-08 14:50 -0700
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-09 00:02 +0000
Re: The � debate Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-05-09 13:10 +1200
Re: The � debate Ben Finney <ben@benfinney.id.au> - 2014-05-09 13:13 +1000
Re: The � debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 01:34 +0000
Re: The � debate Mark H Harris <harrismh777@gmail.com> - 2014-05-09 21:34 -0500
Re: The � debate Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-05-10 17:58 +1200
Re: The � debate Chris Angelico <rosuav@gmail.com> - 2014-05-10 17:10 +1000
Re: The � debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 07:48 +0000
Re: The � debate Chris Angelico <rosuav@gmail.com> - 2014-05-10 18:01 +1000
Re: The � debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-10 11:21 +0300
Re: The � debate Rustom Mody <rustompmody@gmail.com> - 2014-05-10 02:05 -0700
Re: The � debate Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 12:30 -0700
Re: The � debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-10 11:18 +0300
Re: The � debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 09:31 +0000
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 13:18 +0000
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-08 23:46 +1000
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 14:22 +0000
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-09 00:51 +1000
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 16:04 +0000
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-09 02:10 +1000
Re: The “does Python have variables?” debate Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-08 21:02 -0400
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-09 01:32 +0000
Re: The “does Python have variables?” debate Roy Smith <roy@panix.com> - 2014-05-08 22:21 -0400
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-09 12:31 +1000
Re: The "does Python have variables?" debate Rustom Mody <rustompmody@gmail.com> - 2014-05-08 22:40 -0700
Re: The "does Python have variables?" debate Chris Angelico <rosuav@gmail.com> - 2014-05-09 15:51 +1000
Re: The "does Python have variables?" debate Rustom Mody <rustompmody@gmail.com> - 2014-05-09 07:09 -0700
Re: The "does Python have variables?" debate Chris Angelico <rosuav@gmail.com> - 2014-05-10 00:29 +1000
Re: The "does Python have variables?" debate Rustom Mody <rustompmody@gmail.com> - 2014-05-09 09:07 -0700
Re: The “does Python have variables?â€瑩 debate Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-09 19:51 -0400
Re: The “does Python have variables?â€瑩 debate Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-05-10 01:03 +0100
Fortran (Was: The "does Python have variables?" debate) Roy Smith <roy@panix.com> - 2014-05-10 09:42 -0400
Re: Fortran (Was: The "does Python have variables?" debate) Terry Reedy <tjreedy@udel.edu> - 2014-05-10 14:31 -0400
Re: Fortran (Was: The "does Python have variables?" debate) Mark H Harris <harrismh777@gmail.com> - 2014-05-11 01:17 -0500
Re: Fortran (Was: The "does Python have variables?" debate) Rustom Mody <rustompmody@gmail.com> - 2014-05-11 00:01 -0700
Re: Fortran (Was: The "does Python have variables?" debate) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 07:09 +0000
Re: Fortran (Was: The "does Python have variables?" debate) Tomasz Rola <rtomek@ceti.pl> - 2014-05-11 18:09 +0200
Re: Fortran Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 19:27 +0300
Re: Fortran Roy Smith <roy@panix.com> - 2014-05-11 13:51 -0400
Re: Fortran Chris Angelico <rosuav@gmail.com> - 2014-05-12 04:08 +1000
Re: Fortran Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 23:51 +0000
Re: Fortran Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-05-12 01:27 +0100
Re: Fortran Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-12 02:28 +0000
Re: Fortran Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-05-12 10:05 +0100
Re: Fortran Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-12 20:52 -0400
Re: Fortran Ethan Furman <ethan@stoneleaf.us> - 2014-05-11 11:05 -0700
Re: Fortran Chris Angelico <rosuav@gmail.com> - 2014-05-12 04:33 +1000
Re: Fortran Roy Smith <roy@panix.com> - 2014-05-11 14:43 -0400
Re: Fortran Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 23:15 +0000
Re: Fortran MRAB <python@mrabarnett.plus.com> - 2014-05-12 00:51 +0100
Re: Fortran Roy Smith <roy@panix.com> - 2014-05-11 20:14 -0400
Re: Fortran alister <alister.nospam.ware@ntlworld.com> - 2014-05-12 14:14 +0000
Re: Fortran Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-12 01:11 +0000
Re: Fortran Dave Angel <d@davea.name> - 2014-05-11 23:27 -0400
Re: Fortran Grant Edwards <invalid@invalid.invalid> - 2014-05-12 14:07 +0000
Re: Fortran Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-11 21:12 -0400
Re: Fortran (Was: The "does Python have variables?" debate) Chris Angelico <rosuav@gmail.com> - 2014-05-12 02:42 +1000
Re: Fortran Tomasz Rola <rtomek@ceti.pl> - 2014-05-11 20:04 +0200
Re: Fortran Chris Angelico <rosuav@gmail.com> - 2014-05-12 04:12 +1000
Re: Fortran (Was: The "does Python have variables?" debate) Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-05-11 19:05 +0200
Re: Fortran (Was: The "does Python have variables?" debate) Mark H Harris <harrismh777@gmail.com> - 2014-05-11 13:54 -0500
Re: Fortran (Was: The "does Python have variables?" debate) Chris Angelico <rosuav@gmail.com> - 2014-05-12 04:59 +1000
Re: Fortran (Was: The "does Python have variables?" debate) Mark H Harris <harrismh777@gmail.com> - 2014-05-11 14:14 -0500
Re: Fortran (Was: The "does Python have variables?" debate) albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-05-29 14:06 +0000
Re: Fortran (Was: The "does Python have variables?" debate) Peter Pearson <ppearson@nowhere.invalid> - 2014-05-29 17:53 +0000
Re: Fortran (Was: The "does Python have variables?" debate) Dave Angel <davea@davea.name> - 2014-05-11 23:10 -0400
Re: Fortran (Was: The "does Python have variables?" debate) Mark H Harris <harrismh777@gmail.com> - 2014-05-11 23:10 -0500
Re: Fortran (Was: The "does Python have variables?" debate) Mark H Harris <harrismh777@gmail.com> - 2014-05-11 23:26 -0500
Re: Fortran (Was: The "does Python have variables?" debate) Chris Angelico <rosuav@gmail.com> - 2014-05-12 14:53 +1000
Re: Fortran (Was: The "does Python have variables?" debate) Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-05-12 10:44 +0200
Re: Fortran (Was: The "does Python have variables?" debate) Mark H Harris <harrismh777@gmail.com> - 2014-05-13 00:33 -0500
Re: Fortran (Was: The "does Python have variables?" debate) Steven D'Aprano <steve@pearwood.info> - 2014-05-13 05:48 +0000
Re: Fortran (Was: The "does Python have variables?" debate) Mark H Harris <harrismh777@gmail.com> - 2014-05-13 00:55 -0500
Re: Fortran (Was: The "does Python have variables?" debate) Chris Angelico <rosuav@gmail.com> - 2014-05-13 15:56 +1000
Re: Fortran (Was: The "does Python have variables?" debate) Steven D'Aprano <steve@pearwood.info> - 2014-05-13 09:34 +0000
Re: Fortran (Was: The "does Python have variables?" debate) Chris Angelico <rosuav@gmail.com> - 2014-05-13 20:00 +1000
Re: Fortran (Was: The "does Python have variables?" debate) Rustom Mody <rustompmody@gmail.com> - 2014-05-13 03:44 -0700
Re: Fortran (Was: The "does Python have variables?" debate) Chris Angelico <rosuav@gmail.com> - 2014-05-13 20:50 +1000
Re: Fortran (Was: The "does Python have variables?" debate) Gene Heskett <gheskett@wdtv.com> - 2014-05-13 02:31 -0400
Re: Fortran (Was: The "does Python have variables?" debate) Steven D'Aprano <steve@pearwood.info> - 2014-05-13 07:22 +0000
Re: Fortran (Was: The "does Python have variables?" debate) Roy Smith <roy@panix.com> - 2014-05-13 07:16 -0400
Re: Fortran (Was: The "does Python have variables?" debate) Chris Angelico <rosuav@gmail.com> - 2014-05-13 21:21 +1000
Re: Fortran (Was: The "does Python have variables?" debate) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-05-13 14:42 +0100
Re: Fortran (Was: The "does Python have variables?" debate) Gene Heskett <gheskett@wdtv.com> - 2014-05-13 07:42 -0400
Re: Fortran Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-05-13 19:33 +0200
Re: Fortran Marko Rauhamaa <marko@pacujo.net> - 2014-05-13 22:57 +0300
Re: Fortran Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-14 00:10 +0000
Re: Fortran Ian Kelly <ian.g.kelly@gmail.com> - 2014-05-13 21:43 -0600
Re: Fortran Marko Rauhamaa <marko@pacujo.net> - 2014-05-14 07:35 +0300
Re: Fortran Steven D'Aprano <steve@pearwood.info> - 2014-05-14 06:58 +0000
Re: Fortran Marko Rauhamaa <marko@pacujo.net> - 2014-05-14 11:46 +0300
Re: Fortran Sturla Molden <sturla.molden@gmail.com> - 2014-05-14 23:05 +0000
struct.unpack: why 's' fmt char convert to bytestring GuoChao <cx63@outlook.com> - 2014-05-15 20:34 +0800
Re: struct.unpack: why 's' fmt char convert to bytestring Dave Angel <davea@davea.name> - 2014-05-15 09:49 -0400
Re: struct.unpack: why 's' fmt char convert to bytestring MRAB <python@mrabarnett.plus.com> - 2014-05-15 15:47 +0100
Re: Fortran Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-05-14 15:13 +0200
Re: Fortran albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-05-29 14:26 +0000
Re: Fortran Marko Rauhamaa <marko@pacujo.net> - 2014-05-29 17:50 +0300
Re: Fortran Chris Angelico <rosuav@gmail.com> - 2014-05-30 00:58 +1000
Re: Fortran Marko Rauhamaa <marko@pacujo.net> - 2014-05-29 18:09 +0300
Re: Fortran Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-29 17:57 +0000
Re: Fortran Marko Rauhamaa <marko@pacujo.net> - 2014-05-29 21:55 +0300
Re: The “does Python have variables?” debate Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-05-09 09:13 +0100
Re: The “does Python have variables?” debate Michael Torrie <torriem@gmail.com> - 2014-05-08 08:06 -0600
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-09 00:13 +1000
Re: The “does Python have variables?” debate Terry Reedy <tjreedy@udel.edu> - 2014-05-08 15:21 -0400
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 23:06 +0300
Re: The “does Python have variables?” debate Ethan Furman <ethan@stoneleaf.us> - 2014-05-08 15:36 -0700
Re: The “does Python have variables?” debate Ethan Furman <ethan@stoneleaf.us> - 2014-05-08 17:05 -0700
Re: The “does Python have variables?” debate Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-05-09 01:47 +0100
Re: The “does Python have variables?” debate Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 00:57 +0000
Re: The “does Python have variables?” debate Roy Smith <roy@panix.com> - 2014-05-08 08:41 -0400
Re: The “does Python have variables?” debate Chris Angelico <rosuav@gmail.com> - 2014-05-08 22:54 +1000
Re: The “does Python have variables?” debate Ethan Furman <ethan@stoneleaf.us> - 2014-05-08 06:18 -0700
Re: The “does Python have variables?” debate Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 17:03 +0300
Re: The “does Python have variables?” debate Ethan Furman <ethan@stoneleaf.us> - 2014-05-08 16:09 -0700
Re: The “does Python have variables?” debate "Neil D. Cerutti" <neilc@norwich.edu> - 2014-05-08 10:47 -0400
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