README.md

Exercise: StringsAndBinaries-6

Write a function to capitalize the sentences in a string. Each sentence is terminated by a period and a string. Right now, the case of the characters in the string is random.

Solution

See the sentences.exs file for the full module.

They gave us a pretty big hint by telling us each sentence is terminated by a period and a string; now we know what we can split on. Let's start there:

defp do_separate_sentences(paragraph) do
  sentences = String.split(paragraph, ". ")
end

The only problem with this is that by splitting on ". ", we lose those characters so we need to append a period to all but the last sentence.

defp do_separate_sentences(paragraph) do
  sentences = String.split(paragraph, ". ")
  Enum.map sentences, fn sentence ->
    case String.ends_with?(sentence, ".") do
      false -> sentence <> "."
      true -> sentence
    end
  end
end

Okay, now we have separated out the sentences so we can move on to capitalization. The String module provides this for us so all we need to do is:

defp do_capitalize(sentences) do
  Enum.map sentences, fn sentence -> String.capitalize sentence end
end

And finally, we need to bring the sentences back together again:

defp do_join_sentences(sentences) do
  Enum.join sentences, " "
end

Put it all together:

def capitalize(paragraph) do
  paragraph
  |> do_separate_sentences
  |> do_capitalize
  |> do_join_sentences
end

Let's test it:

iex> Sentences.capitalize "oh. a DOG. woof."
"Oh. A dog. Woof."