Do I need to call the Math class directly?

Question

If I'm using a function from the Math module, such as log10, do I need to call Math.log10(number) or can I do number.log10?

Matheus Moreira · Accepted Answer · 2011-03-19T19:29:40.620

3

Numbers have no log10 method available by default, but you can extend the Numeric class to add that functionality:

class Numeric

  def log10
    Math.log10 self
  end
end

10.log10
=> 1.0

If you just want to use the methods without having to write Math all the time, you could include Math, then you can call log10 directly:

class YourClass
  include Math

  def method n
    log10 n
  end
end

YourClass.new.method 10
=> 1.0

edited Mar 19 '11 at 19:29

answered Mar 19 '11 at 19:19

Matheus Moreira

You don't need to require Math to use it. – Michelle Tilley Mar 19 '11 at 19:26
1

@Justin: please take a look at the difference between include and require here: http://stackoverflow.com/questions/318144/what-is-the-difference-between-include-and-require-in-ruby :) – Amokrane Chentir Mar 19 '11 at 19:28
@Justin, I think I misunderstood your question. Please take a look at my updated answer. – Matheus Moreira Mar 19 '11 at 19:32

score 1 · Answer 2 · answered Mar 19 '11 at 19:20

Why don't you just try, using irb for instance? or just this command line:

ruby -e 'puts Math.log10(10)'

1.0

ruby -e 'log10(10)'

-e:1:in <main>': undefined methodlog10' for main:Object (NoMethodError)

I guess you have your answer :)

By the way you can include the Math module:

include Math

to be able to use your log10 method without writing it explicitly everytime:

 ruby -e 'include Math; puts log10(10)'
  => 1.0

2 Answers2