Beefy Boxes and Bandwidth Generously Provided by pair Networks
Your skill will accomplish
what the force of many cannot
 
PerlMonks  

Re: Is this odd behavior a floating point problem?

by Anonymous Monk
on Mar 23, 2012 at 17:02 UTC ( #961263=note: print w/ replies, xml ) Need Help??

Comment on Re: Is this odd behavior a floating point problem?
Re^2: Is this odd behavior a floating point problem?
by wickedjester (Initiate) on Mar 23, 2012 at 17:10 UTC
    Yes, I've seen and skimmed this document, but, not to be rude, but I'm not interested in becoming a computer scientist in order to write a script to do basic math. Adding together 0.001 40 times is pretty basic and if my calculator can do it, I not sure I understand why Perl won't.

      It's not a Perl problem, it's the problem of representing a non-terminating series for base 2 using a finite number of binary digits. You are accustomed to seeing it in base ten when you try to represent 1/3rd, yet I hear no complaints that your ten counting fingers are malfunctioning. Your calculator gets it right by rounding to the eight or ten significant digits that you see on its little LCD display. In other words, it really doesn't get it right; it just covers up the ugliness. And, in fact, I see a nearly identical question every day in reference to C, C++, PHP, and myriad other programming languages over on StackOverflow. It's not a problem unique to Perl.

      I understand that the "What every computer scientist should know..." article is a little beyond what someone who just wants to get the job done might want to digest. That's fine, the article goes into painful details. Try this response (shameless plug, I wrote it), which tries to spell it out in less technical terms: Re: shocking imprecision.


      Dave

      If you don't like the WhatEvery... article -- and I agree that it is written more to impress than inform; and is way over promoted -- then try this. Short, sweet & clear.


      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.

      The start of some sanity?

      If I were doing it with a calculator, I'd surely end up with too many or too few entries of 0.001. I might mess it up building an array. Are you sure you have the right number of elements?

      You can check easily enough:

      say scalar(@arr); # 40 say $#arr; # 39

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://961263]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others meditating upon the Monastery: (9)
As of 2014-09-30 20:08 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    How do you remember the number of days in each month?











    Results (383 votes), past polls