新手问题 Ruby 中 *0.1 和 /10 结果不一样？

thanatos · August 14, 2015 · Last by msg7086 replied at August 14, 2015 · 1626 hits

对于一个浮点型变量执行*0.1 和/10 为啥结果不同？比如 133.3 * 0.1 = 13.33000000000002 而 133.3/10= 13.33

谢谢！

42thcoder #1 August 14, 2015

[68] pry(main)> 133.3/10.0
=> 13.330000000000002

thanatos #2 August 14, 2015

#1 楼 @42thcoder why 啊？那个 2 是啥意思啊？

poshboytl #3 August 14, 2015

你如果追求精确的小数计算应该用 BigDecimal

(BigDecimal.new("133.3")/BigDecimal.new("10.0")).to_f #=> 13.33

# BigDecimal provides similar support for very large or very accurate floating point numbers.

ywjno #4 August 14, 2015

浮点数计算不精确这不是常识么

1 likes

thanatos #5 August 14, 2015

#4 楼 @ywjno 好吧，学到一个常识

msg7086 #6 August 14, 2015

因为 133.3 和 0.1 在二进制下无法精确表示，计算时就会产生细小的误差。

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