57 lines
1.5 KiB
Elixir
57 lines
1.5 KiB
Elixir
defmodule Maps do
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use Koans
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@intro "Maps"
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@person %{
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first_name: "Jon",
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last_name: "Snow",
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age: 27
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}
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koan "Maps represent structured data, like a person" do
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assert @person == %{first_name: ___, last_name: "Snow", age: 27}
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end
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koan "Fetching a value returns a tuple with ok when it exists" do
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assert Map.fetch(@person, :age) == ___
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end
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koan "Or the atom :error when it doesn't" do
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assert Map.fetch(@person, :family) == ___
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end
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koan "Extending a map is as simple as adding a new pair" do
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person_with_hobby = Map.put(@person, :hobby, "Kayaking")
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assert Map.fetch(person_with_hobby, :hobby) == ___
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end
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koan "Put can also overwrite existing values" do
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older_person = Map.put(@person, :age, 37)
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assert Map.fetch(older_person, :age) == ___
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end
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koan "Or you can use some syntactic sugar for existing elements" do
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younger_person = %{@person | age: 16}
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assert Map.fetch(younger_person, :age) == ___
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end
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koan "Can remove pairs by key" do
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without_age = Map.delete(@person, :age)
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assert Map.has_key?(without_age, :age) == ___
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end
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koan "Can merge maps" do
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assert Map.merge(%{first_name: "Jon"}, %{last_name: "Snow"}) == ___
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end
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koan "When merging, the last map wins" do
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merged = Map.merge(@person, %{last_name: "Baratheon"})
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assert Map.fetch(merged, :last_name) == ___
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end
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koan "You can also select sub-maps out of a larger map" do
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assert Map.take(@person, [:first_name, :last_name]) == ___
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end
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end
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