greater_less

GreaterLess

The GreaterLess gem can be used to generate objects that represent halfopen intervals, but transparently behave as Ruby Floats.

Setup

To install, type

sudo gem install greater_less

If you are using bundler, add greater_less to your gemfile

gem 'greater_less'

Getting Started

One easy way to integrate this gem into your project is by requiring the GreaterLess string extension as follows:

require 'greater_less/string_extension'

This extension redifines the #to_f method of the String class:

class String
  alias :to_f_without_greater_less :to_f

  def to_f
    if self =~ GreaterLess::GREATER_LESS
      return GreaterLess.new(self)
    end
    self.to_f_without_greater_less
  end
end

Now when a string starts with a greater or less sign (like for instance "> 3.45"), the #to_f method converts it to a GreaterLess object instead of the value 0.0.

Alternatively you can opt to create GreaterLess objects using initialize directly, like so:

value = GreaterLess.new("> 3.45")

Usage

A GreaterLess object can be compared to a Float (or other numeric) as if it were a Float itself. For instance one can do the following:

>> value = ">3.45".to_f
=> > 3.45
>> value > 2.45
=> true
>> value >= 2.45
=> true
>> 2.45 > value
=> false
>> 2.45 >= value
=> false
>> value == ">3.45".to_f
=> true
>> value != 2.45
=> true

It is also possible to compare GreaterLess objects with each other, so you do not have to worry about what kind of object you are dealing with in your code:

>> value1 = ">3.45".to_f
=> > 3.45
>> value2 = "< 2.45".to_f
=> < 2.45
>> value1 > value2
=> true
>> value2 > value1
=> false

Finally it is possible to apply simple arithmetics to GreaterLess objects like addition, subtraction, multiplication and division:

>> value = ">3.45".to_f
=> > 3.45
>> value + 2
=> > 5.45
>> value - 2
=> > 1.4500000000000002
>> value * 2
=> > 1.725

Inverting the object's sign when multiplying with a negative numerical or using a GreaterLess object in the denominator is nicely dealt with:

>> value = ">3.45".to_f
=> > 3.45
>> -1 * value
=> < -3.45
>> 1 / value
=> < 0.2898550724637681
>> -1 / value
=> > -0.2898550724637681

In many cases it makes no sense to apply the operators +, -, * or / on a pair of GreaterLess objects, so when this happens an exception is raised for now.

All other methods are delegated to the Float value the GreaterLess object contains, so that it transparently acts like a Float. This means you should be careful when using methods like abs or round since they return the result from the underlying Float and bypass the GreaterLess behavior.

Contributing to greater_less

• Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet.
• Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it.
• Fork the project.
• Start a feature/bugfix branch.
• Commit and push until you are happy with your contribution.
• Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
• Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

Copyright

Copyright (c) 2016 Samuel Esposito, Jorn van de Beek. See LICENSE.txt for further details.