Numeric

Checking if a given value is "numeric" is a common problem. How can we do in this Ruby? There are many problematic ways, such as converting to an integer or float or using a regex:

"String".to_i
# => 0

nil.to_f
# => 0.0

:'0'.to_i
# NoMethodError: undefined method `to_i' for :"0":Symbol

"1e5" =~ /^\d*$/
 => nil

This gem defines a simple (and correct) #numeric? method on all Ruby objects. The rules are simple:

• All descendants of Numeric are numeric.
• All strings or symbols that can be converted with Complex() are numeric.
• All other objects are not numeric.

If you want to get more specific, the following methods are also defined:

• #integer?
• #float?
• #decimal?
• #rational?
• #complex?

Note that for these more specific methods, a string that can be converted to a Float (such as '1') will return true for #float?. An instance of a different Numeric class (such as 1, Integer) will return false for #float?.

The gem is tested to work in MRI Ruby 1.9 - 2.0, and JRuby (1.9 mode). All other Rubies are too lax in what their Numeric classes accept, which prevents this gem from working completely.

MRI 2.0.0's BigDecimal class is also too lax in what it accepts, so 'a'.decimal? will unfortunately return true.

Add this line to your application's Gemfile:

gem 'numeric'

And then execute:

$ bundle

Or install it yourself as:

$ gem install numeric

require 'numeric'

3.numeric?
# => true

'1'.numeric?
# => true

'3e10'.numeric?
# => true

:'0'.numeric?
# => true

'abc123'.numeric?
# => false

{}.numeric?
# => false

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request