84 lines
2.3 KiB
Elixir
84 lines
2.3 KiB
Elixir
defmodule Functions do
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use Koans
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def greet(name) do
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"Hello, #{name}!"
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end
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koan "Functions map arguments to outputs" do
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assert greet("World") == ___
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end
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def multiply(a, b), do: a * b
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koan "Single line functions are cool, but mind the comma and the colon!" do
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assert 6 == multiply(2, ___)
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end
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def first(foo, bar), do: "#{foo} and #{bar}"
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def first(foo), do: "Only #{foo}"
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koan "Functions with the same name are distinguished by the number of arguments they take" do
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assert first("One", "Two") == ___
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assert first("One") == ___
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end
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def repeat_again(message, times \\ 5) do
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String.duplicate(message, times)
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end
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koan "Not all arguments are always needed" do
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assert repeat_again("Hello ") == ___
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assert repeat_again("Hello ", 2) == ___
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end
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def sum_up(thing) when is_list(thing), do: :entire_list
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def sum_up(_thing), do: :single_thing
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koan "Functions can be picky and apply only to certain types" do
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assert sum_up([1,2,3]) == ___
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assert sum_up(1) == ___
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end
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def bigger(a,b) when a > b, do: "#{a} is bigger than #{b}"
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def bigger(a,b) when a <= b, do: "#{a} is not bigger than #{b}"
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koan "Intricate guards are possible, but be mindful of the reader" do
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assert bigger(10, 5) == ___
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assert bigger(4, 27) == ___
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end
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def the_length(0), do: "It was zero"
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def the_length(number), do: "The length was #{number}"
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koan "For those individual one-offs, you can even guard on the arguments themselves" do
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assert the_length(0) == ___
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assert the_length(5) == ___
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end
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koan "Little anonymous functions are common, and called with a dot" do
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multiply = fn (a,b) -> a * b end
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assert multiply.(2,3) == ___
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end
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koan "You can even go shorter, by using &(..) and positional arguments" do
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multiply = &(&1 * &2)
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assert multiply.(2,3) == ___
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end
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def times_five_and_then(number, fun), do: fun.(number*5)
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def square(number), do: number * number
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koan "You can pass functions around as arguments. Place an '&' before the name and state the arity" do
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assert times_five_and_then(2, &square/1) == ___
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end
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koan "Functions can be combined elegantly with the pipe operator" do
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result = "full-name"
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|> String.split("-")
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|> Enum.map(&(String.capitalize(&1)))
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|> Enum.join(" ")
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assert result == ___
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end
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end
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