From: Eric Hodel <drbrain@...7.net>
Date: 2011-10-25T09:43:20+09:00
Subject: [ruby-core:40321] [ruby-trunk - Bug #5477][Rejected] to_f function / multiplication bug


Issue #5477 has been updated by Eric Hodel.

Status changed from Open to Rejected

Yes, see also:

http://wiki.github.com/rdp/ruby_tutorials_core/ruby-talk-faq#floats_imprecise
http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems

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Bug #5477: to_f function / multiplication bug
http://redmine.ruby-lang.org/issues/5477

Author: Noto Modungwa
Status: Rejected
Priority: Normal
Assignee: 
Category: core
Target version: 1.9.2
ruby -v: ruby 1.9.2p174 (2011-01-28 revision 30696) [x86_64-darwin10.6.0]


This is posted on stack overflow but I thought I should report it here
Hi I just ran into an issue where ruby's to_f function is giving me inconsistent results.

ruby-1.9.2-head :026 > 8.45.to_f * 100 => 844.9999999999999

ruby-1.9.2-head :027 > 4.45.to_f * 100 => 445.0

ruby-1.9.2-head :028 > 4.35.to_f * 100 => 434.99999999999994

My workaround is to simply round the result this way

ruby-1.9.2-head :029 > (4.35.to_f * 100).round => 435

After more playing around I realised that the issue might be with the multiplication operator "* 100"


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