exercism/elixir/boutique-suggestions/README.md

# Boutique Suggestions

Welcome to Boutique Suggestions on Exercism's Elixir Track.
If you need help running the tests or submitting your code, check out `HELP.md`.
If you get stuck on the exercise, check out `HINTS.md`, but try and solve it without using those first :)

## Introduction

## List Comprehensions

Comprehensions provide a facility for transforming _Enumerables_ easily and declaratively.

To declare a very simple comprehension, we can use the `for` keyword followed by a _generator_ and a _do-block_ which creates the new values from the enumerated values.

```elixir
for n <- [0, 1, 2, 3], do: n + 1
# => [1, 2, 3, 4]
```

Comprehensions can also have _filters_. Values that do not pass the filter are removed from the final list:

```elixir
for n <- [0, 1, 2, 3], n > 1, do: n + 1
# => [3, 4]
```

We can declare more complicated comprehensions over several lines:

```elixir
for {atom, number} <- [a: 1, b: 2, c: 3, d: 4],
    rem(number, 2) == 0 do
  atom
end
# => [:b, :d]
```

A _cartesian product_ can be created using multiple generators. That means that each value generated by the first generator will be paired once with each value generated by the second generator:

```elixir
for x <- [0, 1],
    y <- [0, 1] do
  {x, y}
end
# => [{0, 0}, {0, 1}, {1, 0}, {1, 1}]
```

## Instructions

Your work at the online fashion boutique store continues. You come up with the idea for a website feature where an outfit is suggested to the user. While you want to give lots of suggestions, you don't want to give bad suggestions, so you decide to use a list comprehension since you can easily _generate_ outfit combinations, then _filter_ them by some criteria.

Clothing items are stored as a map:

```elixir
%{
  item_name: "Descriptive Name",
  price: 99.00,
  base_color: "red"
}
```

## 1. Suggest a combination

Implement `get_combinations/3` to take a list of tops, a list of bottoms, and keyword list of options. For now, set options to default to an empty keyword list. The function should return the cartesian product of the lists.

```elixir
tops = [
  %{item_name: "Dress shirt"},
  %{item_name: "Casual shirt"}
]
bottoms = [
  %{item_name: "Jeans"},
  %{item_name: "Dress trousers"}
]
BoutiqueSuggestions.get_combinations(tops, bottoms)
# => [
#      {%{item_name: "Dress shirt"}, %{item_name: "Jeans"}},
#      {%{item_name: "Dress shirt"}, %{item_name: "Dress trousers"}},
#      {%{item_name: "Casual shirt"}, %{item_name: "Jeans"}},
#      {%{item_name: "Casual shirt"}, %{item_name: "Dress trousers"}}
#    ]
```

## 2. Filter out clashing outfits

Each piece of clothing has a `:base_color` field, use this field to filter out all combinations where the top and the bottom have the same base color.

```elixir
tops = [
  %{item_name: "Dress shirt", base_color: "blue"},
  %{item_name: "Casual shirt", base_color: "black"}
]
bottoms = [
  %{item_name: "Jeans", base_color: "blue"},
  %{item_name: "Dress trousers", base_color: "black"}
]
BoutiqueSuggestions.get_combinations(tops, bottoms)
# => [
#      {%{item_name: "Dress shirt", base_color: "blue"},
#       %{item_name: "Dress trousers", base_color: "black"}},
#      {%{item_name: "Casual shirt", base_color: "black"},
#       %{item_name: "Jeans", base_color: "blue"}}
#    ]
```

## 3. Filter by combination price

Each piece of clothing has a `:price` field associated with it. While you want to give lots of suggestions, you want to be able to provide users an opportunity to select a price within their budget. From the keyword list of options, use `:maximum_price` to filter out combinations where the price of the top and bottom exceed the maximum price.

If no maximum_price is specified, the default should be `100.00`

```elixir
tops = [
  %{item_name: "Dress shirt", base_color: "blue", price: 35},
  %{item_name: "Casual shirt", base_color: "black", price: 20}
]
bottoms = [
  %{item_name: "Jeans", base_color: "blue", price: 30},
  %{item_name: "Dress trousers", base_color: "black", price: 75}
]
BoutiqueSuggestions.get_combinations(tops, bottoms, maximum_price: 50)
# => [
#      {%{item_name: "Casual shirt", base_color: "black", price: 20},
#       %{item_name: "Jeans", base_color: "blue", price: 30}}
#    ]
```

## Source

### Created by

- @neenjaw

### Contributed to by

- @angelikatyborska
- @kevpo