edf50fdf80
- Run mix credo --all to identify possible code optimizations - Resolve most of the errors generated by credo such as: - Numbers larger than 9999 should be written with underscores: 58_127 - Modules should have a @moduledoc tag - Comparison will always return true
87 lines
2.4 KiB
Elixir
87 lines
2.4 KiB
Elixir
defmodule Enums do
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@moduledoc false
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use Koans
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@intro "Enums"
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koan "Knowing how many elements are in a list is important for book-keeping" do
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assert Enum.count([1, 2, 3]) == ___
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end
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koan "Depending on the type, it counts pairs" do
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assert Enum.count(%{a: :foo, b: :bar}) == ___
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end
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def less_than_five?(n), do: n < 5
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koan "Elements can have a lot in common" do
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assert Enum.all?([1, 2, 3], &less_than_five?/1) == ___
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assert Enum.all?([4, 6, 8], &less_than_five?/1) == ___
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end
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def even?(n), do: rem(n, 2) == 0
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koan "Sometimes you just want to know if there are any elements fulfilling a condition" do
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assert Enum.any?([1, 2, 3], &even?/1) == ___
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assert Enum.any?([1, 3, 5], &even?/1) == ___
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end
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koan "Sometimes you just want to know if an element is part of the party" do
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input = [1, 2, 3]
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assert Enum.member?(input, 1) == ___
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assert Enum.member?(input, 30) == ___
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end
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def multiply_by_ten(n), do: 10 * n
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koan "Map converts each element of a list by running some function with it" do
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assert Enum.map([1, 2, 3], &multiply_by_ten/1) == ___
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end
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def odd?(n), do: rem(n, 2) == 1
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koan "Filter allows you to only keep what you really care about" do
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assert Enum.filter([1, 2, 3], &odd?/1) == ___
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end
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koan "Reject will help you throw out unwanted cruft" do
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assert Enum.reject([1, 2, 3], &odd?/1) == ___
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end
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koan "You three there, follow me!" do
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assert Enum.take([1, 2, 3, 4, 5], 3) == ___
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end
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koan "You can ask for a lot, but Enum won't hand you more than you give" do
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assert Enum.take([1, 2, 3, 4, 5], 10) == ___
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end
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koan "Just like taking, you can also drop elements" do
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assert Enum.drop([-1, 0, 1, 2, 3], 2) == ___
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end
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koan "Zip-up in pairs!" do
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letters = [:a, :b, :c]
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numbers = [1, 2, 3]
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assert Enum.zip(letters, numbers) == ___
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end
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koan "When you want to find that one pesky element" do
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assert Enum.find([1, 2, 3, 4], &even?/1) == ___
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end
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def divisible_by_five?(n), do: rem(n, 5) == 0
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koan "...but you don't quite find it..." do
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assert Enum.find([1, 2, 3], &divisible_by_five?/1) == ___
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end
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koan "...you can settle for a consolation prize" do
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assert Enum.find([1, 2, 3], :no_such_element, &divisible_by_five?/1) == ___
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end
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koan "Collapse an entire list of elements down to a single one by repeating a function." do
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assert Enum.reduce([1, 2, 3], 0, fn element, accumulator -> element + accumulator end) == ___
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end
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end
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