Addition error with ruby-1.9.2 [duplicate]

问题:

This question already has an answer here:

• ruby: converting from float to integer in ruby produces strange results 3 answers

When I add 0.1+0.2 I am getting 0.30000000000000004 but when I add the same number in ruby 1.8.7 I am getting the correct answer 0.3. I get 0.3 by rounding but I just want to get 0.3 on ruby 1.9.2 by adding 0.1 and 0.2

回答1:

You need bigdecimal for this to make work.

(BigDecimal('0.1') + BigDecimal("0.2")).to_f

See below link:

http://redmine.ruby-lang.org/issues/4394

回答2:

Your old ruby lied to you:

$ ruby -v
ruby 1.8.7 (2010-06-23 patchlevel 299) [x86_64-linux]
$ irb
irb(main):001:0> printf("%40.40f\n", 0.1 + 0.2)
0.3000000000000000444089209850062616169453
=> nil

Floating point numbers are very tricky beasts.