Issue #5321 has been updated by Kenta Murata.


Yusuke Endoh wrote:
> Can you show any actual use case?

I want to create a mathematical function which behaves like 1/x.
This function is defined over real numbers except for zero,
because lim_{x -> +0} 1/x = +inf while lim_{x -> -0} 1/x = -inf.
So I want to raise Math::DomainError for the function with exact zero.
But I don't want to raise the error for inexact zeros, such as 0.0, -0.0,
BigDecimal("0"), and others which are instances of classes I don't know.

If Numeric#inexact? and Numeric#exact? are given,
I can realize the function more easily.

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Feature #5321: Introducing Numeric#exact? and Numeric#inexact?
http://redmine.ruby-lang.org/issues/5321

Author: Kenta Murata
Status: Assigned
Priority: Normal
Assignee: Yukihiro Matsumoto
Category: 
Target version: 


Ruby has several numeric classes such as Integer.
These classes are classified whether their instances represent numbers exactly.
According to this, Integer and Rational are exact, and Float and BigDecimal are inexact because they're always including error.
The exactness of a Complex depends on its real and imaginary parts.

Now, Ruby's numeric classes doesn't provide predicators to investigate the exactness of their instances.
So, if we want to examine whether a number is exactly zero, we must investigate the class of the number.
I want simple way to examine the number exactness.

I propose to introduce Numeric#exact? and/or Numeric#inexact? for resolving this inconvenience.



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