FibonacciEnumerator

This gems adds FibonacciEnumerator, an Enumerable class that makes it possible to efficiently calculate elements of the Fibonacci sequence.

It is an Enumerable object so it can be iterated through using each and implements methods like first, select, map etc.

Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add fibonacci_enumerator

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install fibonacci_enumerator

Usage

Elements of the Fibonacci sequence are calculated using the dynamic programming approach. Instances of FibonacciEnumerator contain a cache that accumulates already calculated elements of the sequence.

You can use the FibonacciEnumerator class directly as an Enumerable object for convenience.

at

The at method aliases as [] can be used to get a particular element of the sequence.

FibonacciEnumerator.at(1) #=> 1
FibonacciEnumerator.at(2) #=> 1
FibonacciEnumerator.at(3) #=> 2
FibonacciEnumerator.at(4) #=> 3
FibonacciEnumerator.at(5) #=> 5
FibonacciEnumerator.at(6) #=> 8

FibonacciEnumerator[1] #=> 1
FibonacciEnumerator[2] #=> 1
FibonacciEnumerator[3] #=> 2
FibonacciEnumerator[4] #=> 3
FibonacciEnumerator[5] #=> 5
FibonacciEnumerator[6] #=> 8

You can also pass a Range.

FibonacciEnumerator.at(4..7) #=> [3, 5, 8, 13]
FibonacciEnumerator[4..7] #=> [3, 5, 8, 13]

each

You can iterate through the Fibonacci series. Keep in mind that it's infinite, so the loop will go on forever unless manually interrupted

FibonacciEnumerator.each do |element|
    puts element
end
# 1
# 1
# 2
# 3
# 8
# ...

select

You can filter elements using select or reject

FibonacciEnumerator.first(25).select(&:even?)
#=> [0, 2, 8, 34, 144, 610, 2584, 10946, 46368]

This class is Enumerable so methods like each, select, reject, take etc are available as well.

Sharing the cache between multiple calculations

When you want to manually get particular elements of the Fibonacci sequence you can save some time by sharing the cache between calculations.

You can do that by creating an instance of FibonacciEnumerator.

fib = FibonacciEnumerator.new

fib[10]
#=> 55
fib[10] # cache is reused, no calculations were necessary!
#=> 55
fib[15] # the first 10 elements were already calculated, so its faster
#=> 610

Instances are also Enumerable objects so methods like each, select, reject, take etc are available as well.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/Verseth/ruby-fibonacci_enumerator.

License

The gem is available as open source under the terms of the MIT License.