Referring to the documentation of BigDecimal class,
参考BigDecimal类的文档,
n,m = a.precsprecreturns number of significant digits (n) and maximum number of significant digits (m) ofa.n,m = a.precs prec返回有效位数(n)和最大有效位数(m)。
I am puzzled by the following output related to BigDecimal.
我对以下与BigDecimal相关的输出感到困惑。
require 'bigdecimal'
BigDecimal.new('1').precs # => [9, 18]
BigDecimal.new(1).precs # => [9, 27]
I cannot figure out why when a String is passed, the maximum number of significant digits is less compared to when a Fixnum is passed.
我无法弄清楚为什么在传递String时,与传递Fixnum时相比,最大有效位数会更少。
Also will it result in any precision issues?
它还会导致任何精度问题吗?
1 个解决方案
#1
3
If you can read C code, you can start at https://github.com/ruby/ruby/blob/trunk/ext/bigdecimal/bigdecimal.c#L2509 - that's the initializer for any BigDecimal object. If you follow that code to the next method, which is BigDecimal_new you'll notice that when passed an integer argument there are a few more steps to go through before allocating and creating an internal big decimal object as opposed to when passing a string argument.
如果您可以阅读C代码,可以从https://github.com/ruby/ruby/blob/trunk/ext/bigdecimal/bigdecimal.c#L2509开始 - 这是任何BigDecimal对象的初始化程序。如果您将该代码跟随下一个方法,即BigDecimal_new,您会注意到,在传递整数参数时,在分配和创建内部大小数对象之前还需要执行一些步骤,而不是在传递字符串参数时。
In any case, you shouldn't worry about loss of precision - the significant digits attributes are more like hints than absolute values. Even the documentation mentions it: The actual number of significant digits used in computation is usually larger than the specified number.
在任何情况下,您都不必担心精度损失 - 有效数字属性更像是提示而不是绝对值。甚至文档都提到它:计算中使用的实际有效位数通常大于指定的数字。
#1
3
If you can read C code, you can start at https://github.com/ruby/ruby/blob/trunk/ext/bigdecimal/bigdecimal.c#L2509 - that's the initializer for any BigDecimal object. If you follow that code to the next method, which is BigDecimal_new you'll notice that when passed an integer argument there are a few more steps to go through before allocating and creating an internal big decimal object as opposed to when passing a string argument.
如果您可以阅读C代码,可以从https://github.com/ruby/ruby/blob/trunk/ext/bigdecimal/bigdecimal.c#L2509开始 - 这是任何BigDecimal对象的初始化程序。如果您将该代码跟随下一个方法,即BigDecimal_new,您会注意到,在传递整数参数时,在分配和创建内部大小数对象之前还需要执行一些步骤,而不是在传递字符串参数时。
In any case, you shouldn't worry about loss of precision - the significant digits attributes are more like hints than absolute values. Even the documentation mentions it: The actual number of significant digits used in computation is usually larger than the specified number.
在任何情况下,您都不必担心精度损失 - 有效数字属性更像是提示而不是绝对值。甚至文档都提到它:计算中使用的实际有效位数通常大于指定的数字。