77 lines
1.7 KiB
Elixir
77 lines
1.7 KiB
Elixir
defmodule PatternMatching do
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use Koans
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koan "One matches one" do
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assert match?(1, :__)
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end
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koan "A pattern can change" do
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a = 1
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assert a = :__
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end
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koan "A pattern can also be strict" do
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a = 1
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assert ^a = :__
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end
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koan "Patterns can be used to pull things apart" do
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[head | tail] = [1,2,3,4]
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assert head == :__
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assert tail == :__
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end
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koan "And then put them back together" do
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head = 1
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tail = [2,3,4]
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assert :__ == [head | tail]
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end
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koan "Some values can be ignored" do
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[_first, _second, third, _fourth] = [1,2,3,4]
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assert third == :__
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end
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koan "Strings come apart just a easily" do
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"Shopping list: " <> items = "Shopping list: eggs, milk"
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assert items == :__
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end
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koan "Patterns show what you really care about" do
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%{make: make} = %{type: "car", year: 2016, make: "Honda", color: "black"}
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assert make == :__
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end
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koan "The pattern can make assertions about what it expects" do
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assert match?([1, _second, _third], :__)
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end
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def make_noise(%{type: "cat"}), do: "Meow"
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def make_noise(%{type: "dog"}), do: "Woof"
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def make_noise(_anything), do: "Eh?"
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koan "Functions can declare what kind of arguments they accept" do
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dog = %{type: "dog", legs: 4, age: 9, color: "brown"}
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cat = %{type: "cat", legs: 4, age: 3, color: "grey"}
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snake = %{type: "snake", legs: 0, age: 20, color: "black"}
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assert make_noise(dog) == :__
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assert make_noise(cat) == :__
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assert make_noise(snake) == :__
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end
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koan "Errors are shaped differently than sucessful results" do
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result = case Map.fetch(%{}, :obviously_not_a_key) do
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:error -> "not present"
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_ -> flunk("I should not happen")
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end
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assert result == :__
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end
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end
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