# StemEx

Porter stemming algorithm implementation in Elixir

The basic philosophy behind this implementation is to map the structure of
Martin Porter's original description of his
[algorithm](http://tartarus.org/~martin/PorterStemmer) as closely as possible
into Elixir.  The code makes liberal use of Elixir's pattern matching facility.
In order for this to work, there is one quirk - the word to be matched must be
reversed before it is stemmed: "hopping" becomes "gnippoh". This is necessary
because Elixir's pattern matching won't work with `stem <> "ing"` but instead
requires `"gni" <> rstem` (where `rstem` is the reversed stem).  Despite this
quirk, the flipping the words allowed us to greatly simplify the rest of the
coding, almost to the point of being a tedious translation of the textual
description of the algorithm.

References:

* [Overview HTML](https://tartarus.org/martin/PorterStemmer                 )
* [Overview Text](https://tartarus.org/martin/PorterStemmer/def.txt         )
* [Test Input   ](https://tartarus.org/martin/PorterStemmer/voc.txt         )
* [Test Output  ](https://tartarus.org/martin/PorterStemmer/output.txt      )
* [Erlang App   ](https://tartarus.org/martin/PorterStemmer/porter.erl      )
* [Erlang App   ](https://tartarus.org/martin/PorterStemmer/conditions.erl  )

## Installation

To install the escript:

`mix escript.install https://raw.githubusercontent.com/andyl/stem_ex/master/stem_ex`

To install the package:

  1. Add `stem_ex` to your list of dependencies in `mix.exs`:

    From Hex:

    ```elixir
    def deps do
      [{:stem_ex, "~> 0.0.1"}]
    end
    ```

    From GitHub:

    ```elixir
    def deps do
      [{:stem_ex, git: "git://github.com/andyl/stem_ex.git"}]
    end
    ```

  2. Ensure `stem_ex` is started before your application:

    ```elixir
    def application do
      [applications: [:stem_ex]]
    end
    ```