80 lines
1.8 KiB
Elixir
80 lines
1.8 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, 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 = 2
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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 = 2
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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 == 1
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assert tail == [2,3,4]
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end
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koan "or put them back together" do
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head = 1
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tail = [2,3,4]
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assert [1,2,3,4] == [head | tail]
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end
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koan "Some values can be irrelevant" do
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[_first, _second, third, _fourth] = [1,2,3,4]
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assert third == 3
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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 == "eggs, milk"
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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 == "Honda"
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end
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koan "the pattern can make assertions about what it expects" do
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the_list = [1, 2, 3]
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assert match?([1, _, _], the_list)
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refute match?([2, _, _], the_list)
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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) == "Woof"
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assert make_noise(cat) == "Meow"
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assert make_noise(snake) == "Eh?"
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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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{:ok, val} -> val
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:error -> "not present"
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end
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assert result == "not present"
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end
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end
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