Re: Floating point calculation problem

From	"Schizoid Man" <schiz_man@21stcentury.com>
Newsgroups	comp.lang.python
Subject	Re: Floating point calculation problem
Date	2013-02-02 15:48 +0000
Organization	A noiseless patient Spider
Message-ID	<kejcfi$s70$1@dont-email.me> (permalink)
References	<keipl5$kif$1@dont-email.me><mailman.1289.1359801291.2939.python-list@python.org><keisev$7v1$1@dont-email.me><mailman.1291.1359804020.2939.python-list@python.org><keitk2$hln$1@dont-email.me><mailman.1292.1359805138.2939.python-list@python.org><keiujd$o71$1@dont-email.me> <mailman.1293.1359806334.2939.python-list@python.org>

Show all headers | View raw

> Ah, there may well be something in that. Definitely post the code and
> outputs; chances are someone'll spot the difference.

Ok, I *think* I found the source of the difference:

This is the base code that runs fine in v 3.3.0 (the output is correct):

def Numer(s, k):
    return math.log(s / k)
s = float(input("Enter s:   "))
k = float(input("Enter k:   "))
print("Result: ", Numer(s, k))

For the v2.7 version, the only difference is the input lines:
s = input("Enter s:   ")
k = input("Enter k:   ")

So for values of s=60 and k=50, the first code returns 0.1823215567939546 
(on the PC), whereas the second returns 0.0 (on the Mac). This this 
expression is evaluated in the numerator, it never returns a divide by zero 
error, and the result of 0 is treated as legitimate.

However, if I cast the v2.7 inputs as float() then it does indeed return the 
right result. But what threw me was that no cast didn't result in a runtime 
error in 2.7, but did in 3.3.

Also, if the cast is necessary, then now exactly does the dynamic typing 
work?

Thanks.

Thread

Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 10:27 +0000
  Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-02 21:34 +1100
    Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 11:14 +0000
      Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-02 22:20 +1100
        Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 11:34 +0000
          Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-02 22:38 +1100
            Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 11:51 +0000
              Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-02 22:58 +1100
                Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 15:48 +0000
                Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 15:54 +0000
                Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-03 03:00 +1100
                Re: Floating point calculation problem Michael Torrie <torriem@gmail.com> - 2013-02-02 11:19 -0700
                Re: Floating point calculation problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-03 12:25 +1100
                Re: Floating point calculation problem Dave Angel <d@davea.name> - 2013-02-02 21:20 -0500
                Re: Floating point calculation problem Michael Torrie <torriem@gmail.com> - 2013-02-02 21:22 -0700
              Re: Floating point calculation problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-02 23:11 +1100
      Re: Floating point calculation problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-02 22:45 +1100
        Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 11:50 +0000
  Re: Floating point calculation problem Chris Rebert <clp2@rebertia.com> - 2013-02-02 02:47 -0800
  Re: Floating point calculation problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-02 23:05 +1100

csiph-web