Question

你们是否知道如何用数学精准确定以下问题?

p RUBY_VERSION # => "1.9.1"
p 0.1%1 # => 0.1
p 1.1%1 # => 0.1
p 90.0%1 # => 0.0
p 90.1%1 # => 0.0999999999999943
p 900.1%1 # => 0.100000000000023

p RUBY_VERSION # => "1.9.2"
p 0.1%1 # => 0.1
p 1.1%1 # => 0.10000000000000009
p 90.0%1 # => 0.0
p 90.1%1 # => 0.09999999999999432
p 900.1%1 # => 0.10000000000002274

Answer 1

Big Decimal

As the man said;

将一定数量的实际数字固定在一定数量的轨道上,需要大致的代表性。

I have however had great success using the BigDecimal class. To quote its intro

鲁比对武断的精度算术提供内在支持。例如:

42**13 -> 1265437718438866624512

BigDecimal为非常大或非常准确的浮动点数字提供类似的支持。

Taking one of your examples;

>> x = BigDecimal.new( 900.1 )
=> #<BigDecimal:101113be8, 0.9001E3 ,8(8)>
>> x % 1
=> #<BigDecimal:10110b498, 0.1E0 ,4(16)>
>> y = x % 1
=> #<BigDecimal:101104760, 0.1E0 ,4(16)>
>> y.to_s
=> "0.1E0"
>> y.to_f
=> 0.1

As you can see, ensuring decent precision is possible but it requires a little bit of effort.

Answer 2

所有电脑语言都是如此,而不仅仅是鲁克语。它是在双轨计算机上显示浮动点数的一个特征:

rel=“nofollow noreferer”> 每个计算机科学家应了解Arithmetic 点

Answer 3

<>0.1>>成浮动点,总是会导致四舍五入的错误。如果你想要确切的解说,请使用 Decimal 。

Big Decimal

友情链接