Let library users bring their own stem function

lib/simple_bayes/trainer/token_stemmer.ex

@@ -1,18 +1,15 @@
 defmodule SimpleBayes.Trainer.TokenStemmer do
   @doc """
-  Stems the word, or passes the word through.
+  Stems the word using `stemmer`. Passes the word through if it is false.
 
   ## Examples
 
-      iex> SimpleBayes.Trainer.TokenStemmer.stem("buying", nil)
-      "buying"
-
       iex> SimpleBayes.Trainer.TokenStemmer.stem("buying", false)
       "buying"
 
-      iex> SimpleBayes.Trainer.TokenStemmer.stem("buying", true)
+      iex> SimpleBayes.Trainer.TokenStemmer.stem("buying", &Stemmer.stem/1)
       "buy"
   """
-  def stem(word, true), do: Stemmer.stem(word)
-  def stem(word, _),    do: word
+  def stem(word, stemmer) when is_function(stemmer), do: stemmer.(word)
+  def stem(word, _), do: word
 end

mix.exs

@@ -17,16 +17,16 @@ defmodule SimpleBayes.Mixfile do
   end
 
   def application do
-    [applications: [:logger, :math, :decimal, :stemmer]]
+    [applications: [:logger, :math, :decimal]]
   end
 
   defp deps do
     [
       {:ex_doc,  ">= 0.0.0", only: :dev},
       {:faker,   ">= 0.0.0", only: :test},
+      {:stemmer, "~> 1.0.0", only: :test},
       {:math,    ">= 0.0.0"},
       {:decimal, ">= 0.0.0"},
-      {:stemmer, "~> 1.0.0"}
     ]
   end
 

test/simple_bayes/model/bernoulli_test.exs

@@ -90,7 +90,7 @@ defmodule SimpleBayes.BernoulliTest do
     end
 
     test "stemming" do
-      result = SimpleBayes.init(model: :bernoulli, stem: true)
+      result = SimpleBayes.init(model: :bernoulli, stem: &Stemmer.stem/1)
                |> SimpleBayes.train(:apple, "buying apple")
                |> SimpleBayes.train(:banana, "buy banana")
                |> SimpleBayes.classify("buy apple")

test/simple_bayes/model/binarized_multinomial_test.exs

@@ -77,7 +77,7 @@ defmodule SimpleBayes.BinarizedMultinomialTest do
     end
 
     test "stemming" do
-      result = SimpleBayes.init(model: :binarized_multinomial, stem: true)
+      result = SimpleBayes.init(model: :binarized_multinomial, stem: &Stemmer.stem/1)
                |> SimpleBayes.train(:apple, "buying apple")
                |> SimpleBayes.train(:banana, "buy banana")
                |> SimpleBayes.classify("buy apple")

test/simple_bayes/model/multinomial_test.exs

@@ -55,7 +55,7 @@ defmodule SimpleBayes.MultinomialTest do
     end
 
     test "stemming" do
-      result = SimpleBayes.init(stem: true)
+      result = SimpleBayes.init(stem: &Stemmer.stem/1)
                |> SimpleBayes.train(:apple, "buying apple")
                |> SimpleBayes.train(:banana, "buy banana")
                |> SimpleBayes.classify("buy apple")