math - Avoiding problems with JavaScript's weird decimal calculations -


i just read on mdn 1 of quirks of js's handling of numbers due being "double-precision 64-bit format ieee 754 values" when .2 + .1 0.30000000000000004 (that's article reads, 0.29999999999999993 in firefox). therefore:

(.2 + .1) * 10 == 3

evaluates false.

this seems problematic. can done avoid bugs due imprecise decimal calculations in js?

i've noticed if 1.2 + 1.1 right answer. should avoid kind of math involves values less 1? because seems impractical. there other dangers doing math in js?

edit:
understand many decimal fractions can't stored binary, way other languages i've encountered appear deal error (like js handles numbers greater 1) seems more intuitive, i'm not used this, why want see how other programmers deal these calculations.

in situations these tipically rather make use of epsilon estimation.

something (pseudo code)

if (abs(((.2 + .1) * 10) - 3) > epsilon)

where epsilon 0.00000001, or whatever precision require.

have quick read @ comparing floating point numbers


Comments

Post a Comment

Popular posts from this blog

apache - Add omitted ? to URLs -

i working on website cms reads page name of query string, e.g. http://exmaple.com/?pagename . trying create rewrite rule rewrite ? . so, user types in /pagename , taken /?pagename try this: rewriteengine on rewritecond %{request_filename} !-d rewritecond %{request_filename} !-f rewriterule ^/?(.*) index.php?$1 [l]
Read more

redirect - bbPress Forum - rewrite to wwww.mysite prohibits login -

i using bbpress installation without wordpress integration. the redirect of rewriteengine @ forum site works: rewriteengine on rewritecond %{http_host} ^forum.mysite.com$ rewriterule (.*)$ http://www.forum.mysite.com/$1 [r=301,l] the problem login pppress. bbpress login not recognize: http://www.forum.mysite/bb-login.php . it redirects to: http://forum.mysite.com/bb-login.php . i tried permalink settings none , name based, same issue. does uses redirect in bbpress or how can eliminate "double" content , redirect permanently www.? i redirected www.forum.mysite.com forum.mysite.com , achieved eliminate "double" content.
Read more

php - How can I stop spam on my custom forum/blog? -

so have custom built forum & blog system of late has been dealing lot of spam. if wordpress use akismet, if different common platform i'm sure i'd find plugin. there kind of static class can download this? using php. i'd still go akismet, if it. uses outside of wordpress, may have pay fee it, depending on use -- check terms , conditions -- it's option , easy implement in php using api. use api key wordpress. com account access. basically, grab whichever php client library takes fancy -- use alex potsides' php5 library -- plug in key, , it's handful of lines of code. here's bare bones of validation straight 1 of live sites: ... if ($akismet) { $akismet->setcommentauthor($name); $akismet->setcommentauthoremail($session->userinfo["email"]); $akismet->setcommentauthorurl(""); $akismet->setcommentcontent($sentence);...
Read more