# Fibonaccia

*As though there weren’t enough Ruby gems for dealing with the Fibonacci sequence.. here’s another one!*

`Fibonaccia`

is a very simple package for accessing the series of
Fibonacci numbers.

`Fibonaccia`

also provides the irrational constant `PHI`

(`φ`

), which
represents the Golden Ratio
bu which isn’t in Ruby’s own *Math* module.

You can request a specific term in the Fibonacci series:

```
thirty_fifth = Fibonaccia[35]
```

or a slice:

```
fourth_through_seventh = Fibonaccia[4, 3]
fourth_through_seventh = Fibonaccia.slice(4, 3)
```

or the complete series as far as the module has been requested to derive it:

```
series_so_far = Fibonaccia.series
```

or the number of terms in the series-so-far:

```
term_count = Fibonaccia.terms
```

or check to see if an arbitrary integer is a Fibonacci number:

```
Fibonaccia.is_fibonacci?(354224848179261915075)
=> true
Fibonaccia.is_fibonacci?(354224848179261915075 + 1)
=> false
```

`Fibonaccia`

attempts to be memory-efficient by only deriving the
series to the extent needed by the caller (*i.e.*, if you ask for the
tenth Fibonacci number, `Fibonaccia`

will internally extend its series
to eleven terms if it hasn’t already; if you then ask for the eighth
number, it will return the value from the already-extended internal
series).

```
Fibonaccia.series
=> [ 0, 1, 1 ]
Fibonaccia.terms
=> 3
Fibonaccia[12]
=> 144
Fibonaccia.series
=> [ 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144 ]
Fibonaccia.terms
=> 13
Fibonaccia[8]
=> 21
Fibonaccia.series
=> [ 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144 ]
Fibonaccia.terms
=> 13
```

If memory becomes a concern, you can trim the internal series back to the initial three terms:

```
Fibonaccia.reset
Fibonaccia.terms
=> 3
```

You can grow or shrink the list by any number of terms (although you
**cannot** shrink it to fewer than 3):

```
Fibonaccia.terms
=> 3
Fibonaccia.grow(20)
=> 23
Fibonaccia.terms
=> 23
Fibonaccia.shrink(10)
=> 13
Fibonaccia.terms
=> 13
```

or you can set the size of the series to any arbitrary number of terms (again, you cannot set the series to fewer than 3 terms):

```
Fibonaccia.reset
Fibonaccia.terms
=> 3
Fibonaccia.terms = 2048
Fibonaccia.terms
=> 2048
```

## Plans for the Future

I intend to extend this module in the near future to allow requesting arrays of coördinates along a golden spiral, either polar or rectangular.

And who knows what other features may occur.

## Installation

Add this line to your application’s Gemfile:

```
ruby
gem('fibonaccia')
```

And then execute:

```
$ bundle
```

Or install it yourself as:

```
$ gem install fibonaccia
```

## Usage

```ruby require(‘fibonaccia’)

```

## TODO

- Provide interface for obtaining coördinates on a golden spiral.

## Contributing

- Fork it ( https://github.com/RoUS/fibonaccia/fork )
- Create your feature branch (
`git checkout -b my-new-feature`

) - Commit your changes (
`git commit -am 'Add some feature'`

) - Push to the branch (
`git push origin my-new-feature`

) - Create a new Pull Request

## Licence

`Fibonaccia`

is copyright © 2015 by Ken Coar, and is made available
under the terms of the Apache Licence 2.0:

``` Copyright © 2015 Ken Coar

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

```
http://www.apache.org/licenses/LICENSE-2.0
```

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. ```