> For the complete documentation index, see [llms.txt](https://elixir.petrolidas.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://elixir.petrolidas.com/exhort/day-14.md).

# Day 14

## Exercises

* [x] [Boutique Inventory](#boutique-inventory)

### Boutique Inventory

[Boutique Inventory in Elixir on Exercism](https://exercism.org/tracks/elixir/exercises/boutique-inventory) **|** [View my solution](https://exercism.org/tracks/elixir/exercises/boutique-inventory/solutions/petros)

#### Solution

<details>

<summary>Expand to see code (spoiler alert)</summary>

{% code lineNumbers="true" %}

```elixir
defmodule BoutiqueInventory do
  def sort_by_price(inventory) do
    inventory
    |> Enum.sort_by(&(&1.price))
  end

  def with_missing_price(inventory) do
    inventory
    |> Enum.filter(&is_nil(&1.price))
  end

  def update_names(inventory, old_word, new_word) do
    inventory
    |> Enum.map(&replace_word(&1, old_word, new_word))
  end

  defp replace_word(map, old_word, new_word) do
    name = String.replace(map.name, old_word, new_word)
    Map.put(map, :name, name)
  end

  def increase_quantity(item, count) do
    qbs = Map.new(item.quantity_by_size, fn {k, v} -> {k, v + count} end)
    %{item | quantity_by_size: qbs }
  end

  def total_quantity(item) do
    item.quantity_by_size
    |> Enum.reduce(0, fn {_, v}, sum -> sum + v end)
  end
end
```

{% endcode %}

[View gist on GitHub](https://gist.github.com/petros/809098bdb9b12a6b3def38b291e7f05e)

</details>

#### Notes

Oh Zeus. I really struggled with this one. And it was so simple. I don't know why. Here's my accepted solution:

```elixir
def increase_quantity(item, count) do
  qbs = Map.new(item.quantity_by_size, fn {k, v} -> {k, v + count} end)
  %{item | quantity_by_size: qbs }
end
```

I was trying all sorts of irrelevant things :grimacing:. I was also thrown off by the mention of `Enum.into` in `README.md`. I guess it was an alternative to `Map.new`?\
\
For `total_quantity/1`, I used a different approach, while the exercise recommended `Enum.reduce`. It was the purpose of the exercise to teach you that. My initial implementation was:

```elixir
item.quantity_by_size
|> Map.values
|> Enum.sum
```

I think it's a little easier in the eyes, but I have no idea if it's slower as I am calling a `Map` function and then an `Enum` function. Whereas `reduce/3` is one function.

## Overall progress

<figure><img src="/files/UQqPBFzpi31rjQ2mdvsx" alt="An image showing my progress on Exercism. It&#x27;s 15.4% as of Sunday, 21 August 2022."><figcaption><p>Progress</p></figcaption></figure>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://elixir.petrolidas.com/exhort/day-14.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.