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author | Thomas Letan <contact@thomasletan.fr> | 2017-05-04 08:24:58 +0200 |
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committer | Thomas Letan <contact@thomasletan.fr> | 2017-05-04 08:24:58 +0200 |
commit | 6615da8e2575ae731962ca84461e894f602e51ca (patch) | |
tree | 4ac1018355bbc56dfe4ea2c6b084bc1119c8535a |
release: lkn-prelude-0.1.0
-rw-r--r-- | .gitignore | 5 | ||||
-rw-r--r-- | LICENSE | 621 | ||||
-rw-r--r-- | README.md | 68 | ||||
-rw-r--r-- | config/config.exs | 1 | ||||
-rw-r--r-- | lib/lkn/prelude.ex | 89 | ||||
-rw-r--r-- | lib/lkn/prelude/option.ex | 158 | ||||
-rw-r--r-- | mix.exs | 76 | ||||
-rw-r--r-- | test/lkn_prelude_test.exs | 6 | ||||
-rw-r--r-- | test/test_helper.exs | 1 |
9 files changed, 1025 insertions, 0 deletions
diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..0af9d2e --- /dev/null +++ b/.gitignore @@ -0,0 +1,5 @@ +_build/ +cover/ +doc/ +deps/ +mix.lock
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Interpretation of Sections 15 and 16. + + If the disclaimer of warranty and limitation of liability provided +above cannot be given local legal effect according to their terms, +reviewing courts shall apply local law that most closely approximates +an absolute waiver of all civil liability in connection with the +Program, unless a warranty or assumption of liability accompanies a +copy of the Program in return for a fee. + + END OF TERMS AND CONDITIONS diff --git a/README.md b/README.md new file mode 100644 index 0000000..d859529 --- /dev/null +++ b/README.md @@ -0,0 +1,68 @@ +# lkn-prelude + +This package is an opinionated Prelude for the [lkn project](http://lkn.ist). It +is designed to fit lkn needs, but if it brings you what you need, feel free to +use it. + +## Guide + +Every module of this package is in the `Lkn.Prelude` namespace to avoid name +collision. If one want to adopt our opinionated point of view, all she has to do +is to add the following line to her code: + +```elixir +use Lkn.Prelude +``` + +After that, the modules are aliased and required, which means they can be used +painlessly. + +## Prelude’s Principles + +### Opaque data-structures and macro-based pattern matching + +In Elixir, it is not rare to see the most common data structure defined as +tuples. For instance, a computation that may or may not return a result will +effectively return `{ :ok, val } | :error`. As a consequence, the caller will +have to match the result: + +```elixir +case res do + {:ok, val} -> + # ... + _ -> + # ... +end +``` + +From our perspective, it brings several issues. The main one is +inconsistency. Some code might return `{:ok, val}` in case of success where +other would return `{:some, val}`. Another is that it makes it harder to change +the data structure implementation. For instance, what if one want to return a +structure rather than a tuple, in order to implement the `Enumerable` protocol? + +This package takes another path. The data structure typespecs are opaque and the +constructors are implemented as macros. The main benefit is macros can be used +to match a value. + +```elixir +case res do + Option.some(x) -> + # ... + Option.nothing() -> + # ... +end +``` + +### Parameterized Typespecs + +Most of the time, the data structure typespecs in Elixir are not parameterized +by the type of the content. In this package, they are. In addition, the data +structure modules define two types: `a` and `b` which are aliases to `any`. From +dialyzer point of view, they bring no additional information and mixing them +does not raise any warning. However, from a developer point of view, it can +bring more information about the real behaviour of a function: + +That is, we believe `@spec map(t(a), (a -> b)) :: t(b)` is more expressive and +useful than `@spec map(t(any), (any -> any)) :: t(any)` or `@spec map(t, (any -> +any)) :: t`. diff --git a/config/config.exs b/config/config.exs new file mode 100644 index 0000000..d2d855e --- /dev/null +++ b/config/config.exs @@ -0,0 +1 @@ +use Mix.Config diff --git a/lib/lkn/prelude.ex b/lib/lkn/prelude.ex new file mode 100644 index 0000000..02665b2 --- /dev/null +++ b/lib/lkn/prelude.ex @@ -0,0 +1,89 @@ +# lkn_prelude: an opiniated prelude for the lkn project +# Copyright (C) 2017 Thomas Letan +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +defmodule Lkn.Prelude do + @moduledoc """ + An opinionated Prelude for the [lkn project](http://lkn.ist). + + It is designed to fit lkn needs, but if it brings you what you need, + feel free to use it. + + ## Guide + + Every module of this package is in the `Lkn.Prelude` namespace to + avoid name collision. If one want to adopt our opinionated point of + view, all she has to do is to add the following line to her code: + + use Lkn.Prelude + + After that, the modules are aliased and required, which means they + can be used painlessly. + + ## Prelude’s Principles + + ### Opaque data-structures and macro-based pattern matching + + In Elixir, it is not rare to see the most common data structure + defined as tuples. For instance, a computation that may or may not + return a result will effectively return `{ :ok, val } | :error`. As + a consequence, the caller will have to match the result: + + case res do + {:ok, val} -> + # ... + _ -> + # ... + end + + From our perspective, it brings several issues. The main one is + inconsistency. Some code might return `{:ok, val}` in case of + success where other would return `{:some, val}`. Another is that it + makes it harder to change the data structure implementation. For + instance, what if one want to return a structure rather than a + tuple, in order to implement the `Enumerable` protocol? + + This package takes another path. The data structure typespecs are + opaque and the constructors are implemented as macros. The main + benefit is macros can be used to match a value. + + case res do + Option.some(x) -> + # ... + Option.nothing() -> + # ... + end + + ### Parameterized Typespecs + + Most of the time, the data structure typespecs in Elixir are not + parameterized by the type of the content. In this package, they + are. In addition, the data structure modules define two types: `a` + and `b` which are aliases to `any`. From dialyzer point of view, + they bring no additional information and mixing them does not raise + any warning. However, from a developer point of view, it can bring + more information about the real behaviour of a function: + + That is, we believe `@spec map(t(a), (a -> b)) :: t(b)` is more + expressive and useful than `@spec map(t(any), (any -> any)) :: + t(any)` or `@spec map(t, (any -> any)) :: t`. + """ + + defmacro __using__(_) do + quote do + alias Lkn.Prelude.Option + require Option + end + end +end diff --git a/lib/lkn/prelude/option.ex b/lib/lkn/prelude/option.ex new file mode 100644 index 0000000..17bc334 --- /dev/null +++ b/lib/lkn/prelude/option.ex @@ -0,0 +1,158 @@ +# lkn_prelude: an opiniated prelude for the lkn project +# Copyright (C) 2017 Thomas Letan +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +defmodule Lkn.Prelude.Option do + @moduledoc """ + An optional value. + + Whenever a function may or may not returns a value, the Option + macros should be used. In a similar manner, these macros should be + used in pattern matching blocks. This way, the inner representation + can change without the refactoring pain. + + The best way to use this module is by calling `use + Lkn.Prelude`. This call aliases and requires each components of the + lkn Prelude, including this module. + + ## Example + + use Lkn.Prelude + + x = Option.some(3) + y = Option.nothing() + + Option.unwrap(x, 1) + #=> 3 + Option.unwrap!(x) + #=> 3 + Option.unwrap(y, 1) + #=> 1 + """ + + @typedoc """ + The result of a computation which could have returned something but + didn't. + """ + @opaque nothing() :: :nothing + + @typedoc """ + The result of a computation which could have failed to return + something but didn't. + """ + @opaque some(x) :: {:some, x} + + @typedoc """ + The result of a computation which could have failed or could have + returned something. + """ + @type t(x) :: some(x)|nothing + + @typedoc """ + The type of an optional value, before a computation. + """ + @type a() :: any() + + @typedoc """ + The type of an optional value, after a computation. + """ + @type b() :: any() + + @spec some(a) :: some(a) + @doc """ + A macro to create and match an optional value. + """ + defmacro some(x) do + quote do + {:some, unquote(x)} + end + end + + @spec nothing() :: nothing + @doc """ + A macro to create and match a nothing value. + """ + defmacro nothing do + quote do + :nothing + end + end + + @doc """ + A macro to execute a block only if the given optional value exists. + + In `expression`, one can use `x`: it gets the value encapsulated in + `opt`. + """ + defmacro inside(opt, x, do: expression) do + quote do + case unquote(opt) do + unquote(some(x)) -> unquote(expression) + unquote(nothing()) -> :ok + end + end + end + + @spec unwrap(t(a), a) :: a + @doc """ + Get the value contained within a `Lkn.Prelude.Option` or a + default value. + + iex> Lkn.Prelude.Option.unwrap(Lkn.Prelude.Option.some(3), 1) + 3 + iex> Lkn.Prelude.Option.unwrap(Lkn.Prelude.Option.nothing(), 1) + 1 + """ + def unwrap(x, default) do + case x do + some(i) -> i + nothing() -> default + end + end + + @spec unwrap!(some(a)) :: a + @doc """ + Same as `Lkn.Prelude.Option.unwrap/2`, but panicked if there is no + value to unwrap. + + iex> Lkn.Prelude.Option.unwrap!(Lkn.Prelude.Option.some(3)) + 3 + iex> try do + ...> Lkn.Prelude.Option.unwrap!(Lkn.Prelude.Option.nothing()) + ...> rescue + ...> _ -> :ok + ...> end + :ok + """ + def unwrap!(some(x)) do + x + end + def unwrap!(nothing()) do + raise ArgumentError, "Trying to unwrap a `nothing` value" + end + + @spec map(t(a), (a -> b)) :: t(b) + @doc """ + Apply a function to an optional value if it exists. + + iex> Lkn.Prelude.Option.map(Lkn.Prelude.Option.some(3), &(&1 + 1)) + Lkn.Prelude.Option.some(4) + """ + def map(some(x), f) do + some(f.(x)) + end + def map(nothing(), _f) do + nothing() + end +end @@ -0,0 +1,76 @@ +defmodule LknPrelude.Mixfile do + use Mix.Project + + def project do + [ + app: :lkn_prelude, + name: "lkn-prelude", + version: "0.1.0", + elixir: "~> 1.4", + deps: deps(), + build_embedded: Mix.env == :prod, + start_permanent: Mix.env == :prod, + deps: deps(), + description: description(), + source_url: "https://nest.pijul.com/lthms/lkn-prelude:lkn-prelude-0.1.0", + package: package(), + test_coverage: [ + tool: ExCoveralls + ], + preferred_cli_env: [ + "coveralls": :test, + "coveralls.detail": :test, + "coveralls.post": :test, + "coveralls.html": :test, + ], + dialyzer: [ + flags: [ + "-Wunmatched_returns", + :error_handling, + :race_conditions, + :underspecs, + ], + ], + ] + end + + def application do + [] + end + + def description do + """ + An opiniated yet generic prelude for lkn. + """ + end + + defp deps do + [ + {:credo, "~> 0.4", only: [:dev, :test], runtime: false}, + {:dialyxir, "~> 0.5", only: :dev, runtime: false}, + {:ex_doc, "~> 0.15", only: :dev, runtime: false}, + {:excoveralls, "~> 0.6", only: :test, runtime: false}, + ] + end + + defp package do + [ + name: :lkn_prelude, + files: [ + "lib", + "mix.exs", + "README.md", + "LICENSE", + ], + maintainers: [ + "Thomas Letan" + ], + licenses: [ + "GPL 3.0" + ], + links: %{ + "Pijul Nest" => "https://nest.pijul.com/lthms/lkn-prelude:lkn-prelude-0.1.0", + }, + ] + end +end diff --git a/test/lkn_prelude_test.exs b/test/lkn_prelude_test.exs new file mode 100644 index 0000000..0779da1 --- /dev/null +++ b/test/lkn_prelude_test.exs @@ -0,0 +1,6 @@ +defmodule LknPreludeTest do + use ExUnit.Case + use Lkn.Prelude + + doctest Option +end diff --git a/test/test_helper.exs b/test/test_helper.exs new file mode 100644 index 0000000..869559e --- /dev/null +++ b/test/test_helper.exs @@ -0,0 +1 @@ +ExUnit.start() |