Add lists concept

concepts/lists/about.md

@@ -56,32 +56,32 @@ There are several common Prelude functions for lists:
 - [`head`][head] returns the _head_ of a list -- the _first_ item in a list.
 - [`tail`][tail] returns the _tail_ of the list -- the list _minus_ the _first_ item.
 - [`length`][length] returns the number items in the list.
-- [`elem`][in] returns a boolean value indicating whether the item is an element in the list.
+- [`elem`][elem] returns a boolean value indicating whether the item is an element in the list.
 
-There is also the [`List` module][list].
+There is also the [`Data.List` module][list].
 
-Lists can only contain one data type.
+## List types
+
+In Haskell, lists are **homogenous**.
+This means that all elements of a list have the same type.
+When you try to put elements of different types into the same list, you will get a type error.
 
 ```haskell
 list = [1, "string"]
 -- Error: No instance for (Num String) arising from the literal ‘1’
 ```
 
-## Type annotation
-
 The type annotation of a list is `[a]` where a is the type which the lists holds, for example `String` or `Int`.
 
 ``` haskell
 a :: [Int] 
 a = [1, 2, 3]
 ```
 
-[enum]: https://hexdocs.pm/elixir/Enum.html
-[enum-protocol]: https://hexdocs.pm/elixir/Enumerable.html
-[hd]: https://hexdocs.pm/elixir/Kernel.html#hd/1
-[in]: https://hexdocs.pm/elixir/Kernel.html#in/2
-[length]: https://hexdocs.pm/elixir/Kernel.html#length/1
-[list]: https://hexdocs.pm/elixir/List.html
-[stream]: https://hexdocs.pm/elixir/Stream.html
-[tl]: https://hexdocs.pm/elixir/Kernel.html#tl/1
+[prelude]: https://hackage.haskell.org/package/base/docs/Prelude.html
+[list]: https://hackage.haskell.org/package/base/docs/Data-List.html
+[head]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:head
+[tail]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:tail
+[elem]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:elem
+[length]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:length
 [linked-list-wiki]: https://en.wikipedia.org/wiki/Linked_list

concepts/lists/introduction.md

@@ -34,7 +34,7 @@ Head-tail notation can be used to append items to a list.
 list = [2, 1]
 
 [3, 2, 1] == 3 : list
--- true
+-- -> True
 ```
 
 Appending elements to a list during iteration is considered an anti-pattern. 
@@ -56,32 +56,32 @@ There are several common Prelude functions for lists:
 - [`head`][head] returns the _head_ of a list -- the _first_ item in a list.
 - [`tail`][tail] returns the _tail_ of the list -- the list _minus_ the _first_ item.
 - [`length`][length] returns the number items in the list.
-- [`elem`][in] returns a boolean value indicating whether the item is an element in the list.
+- [`elem`][elem] returns a boolean value indicating whether the item is an element in the list.
 
-There is also the [`List` module][list].
+There is also the [`Data.List` module][list].
 
-Lists can only contain one data type.
+## List types
+
+In Haskell, lists are **homogenous**.
+This means that all elements of a list have the same type.
+When you try to put elements of different types into the same list, you will get a type error.
 
 ```haskell
 list = [1, "string"]
 -- Error: No instance for (Num String) arising from the literal ‘1’
 ```
 
-## Type annotation
-
 The type annotation of a list is `[a]` where a is the type which the lists holds, for example `String` or `Int`.
 
 ``` haskell
 a :: [Int] 
 a = [1, 2, 3]
 ```
 
-[enum]: https://hexdocs.pm/elixir/Enum.html
-[enum-protocol]: https://hexdocs.pm/elixir/Enumerable.html
-[hd]: https://hexdocs.pm/elixir/Kernel.html#hd/1
-[in]: https://hexdocs.pm/elixir/Kernel.html#in/2
-[length]: https://hexdocs.pm/elixir/Kernel.html#length/1
-[list]: https://hexdocs.pm/elixir/List.html
-[stream]: https://hexdocs.pm/elixir/Stream.html
-[tl]: https://hexdocs.pm/elixir/Kernel.html#tl/1
+[prelude]: https://hackage.haskell.org/package/base/docs/Prelude.html
+[list]: https://hackage.haskell.org/package/base/docs/Data-List.html
+[head]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:head
+[tail]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:tail
+[elem]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:elem
+[length]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:length
 [linked-list-wiki]: https://en.wikipedia.org/wiki/Linked_list

concepts/lists/links.json

@@ -1 +1,10 @@
-[]
+[
+    {
+        "url": "https://hackage.haskell.org/package/base/docs/Data-List.html",
+        "description": "Haskell Prelude: Data.List"
+    },
+    {
+        "url": "https://www.haskelltutorials.com/guides/haskell-lists-ultimate-guide.html",
+        "description": "Haskell Lists: The Ultimate Guide"
+    }
+]

config.json

@@ -48,6 +48,18 @@
           "basics"
         ]
       },
+      {
+        "slug": "language-list",
+        "name": "Language List",
+        "uuid": "2770e2c0-883d-4336-be94-3b4ae7529ac3",
+        "prerequisites": [
+          "basics"
+        ],
+        "status": "beta",
+        "concepts": [
+          "lists"
+        ]
+      },
       {
         "slug": "temperature",
         "name": "Temperature",
@@ -1399,6 +1411,11 @@
       "slug": "booleans",
       "name": "Booleans"
     },
+    {
+      "uuid": "ef484ab5-d4d2-4d7c-b4b5-abb5920f916a",
+      "slug": "lists",
+      "name": "Lists"
+    },
     {
       "uuid": "ca21a553-6fc1-49be-8f47-730f97330862",
       "slug": "pattern-matching-literals",

exercises/concept/language-list/.docs/hints.md

@@ -1,8 +1,36 @@
-# General
+# Hints
 
-- Basic numbers operators are described in the Haskell [GHC.Num module documentation](https://hackage.haskell.org/package/base-4.16.0.0/docs/GHC-Num.html). But you might prefer a more easily digestable [basic introduction.](https://www.tutorialspoint.com/haskell/haskell_basic_operators.htm)
+## General
 
-# Modules and Indentation
+- Use the built-in [(linked) list type][list].
 
-- [Declaring modules](https://learnyouahaskell.github.io/modules#making-our-own-modules)
-- [Indentation rules](https://en.wikibooks.org/wiki/Haskell/Indentation)
+## 1. Define a function to return an empty language list
+
+- The function needs to return `[]`.
+
+## 2. Define a function to add a language to the list
+
+- An element can be prepended to a list using `:`.
+
+## 3. Define a function to remove a language from the list
+
+- Haskell [provides a function][tail] to return a list with the first item removed.
+
+## 4. Define a function to return the first item in the list
+
+- HaskellHaskell [provides a function][head] to get the first item from a list.
+
+## 5. Define a function to return how many languages are in the list
+
+- Haskell [provides a function][length] to count the length of a list.
+
+## 6. Define a function to determine if the list includes a functional language
+
+- Your function should return a boolean value indicating whether `"Haskell"` is a member of the list. 
+  Haskell [provides a function][elem] to test list membership.
+
+[list]: https://hackage.haskell.org/package/base/docs/Data-List.html
+[head]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:head
+[tail]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:tail
+[elem]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:elem
+[length]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:length

exercises/concept/language-list/.docs/introduction.md

@@ -56,32 +56,32 @@ There are several common Prelude functions for lists:
 - [`head`][head] returns the _head_ of a list -- the _first_ item in a list.
 - [`tail`][tail] returns the _tail_ of the list -- the list _minus_ the _first_ item.
 - [`length`][length] returns the number items in the list.
-- [`elem`][in] returns a boolean value indicating whether the item is an element in the list.
+- [`elem`][elem] returns a boolean value indicating whether the item is an element in the list.
 
-There is also the [`List` module][list].
+There is also the [`Data.List` module][list].
 
-Lists can only contain one data type.
+## List types
+
+In Haskell, lists are **homogenous**.
+This means that all elements of a list have the same type.
+When you try to put elements of different types into the same list, you will get a type error.
 
 ```haskell
 list = [1, "string"]
 -- Error: No instance for (Num String) arising from the literal ‘1’
 ```
 
-## Type annotation
-
 The type annotation of a list is `[a]` where a is the type which the lists holds, for example `String` or `Int`.
 
 ``` haskell
 a :: [Int] 
 a = [1, 2, 3]
 ```
 
-[enum]: https://hexdocs.pm/elixir/Enum.html
-[enum-protocol]: https://hexdocs.pm/elixir/Enumerable.html
-[hd]: https://hexdocs.pm/elixir/Kernel.html#hd/1
-[in]: https://hexdocs.pm/elixir/Kernel.html#in/2
-[length]: https://hexdocs.pm/elixir/Kernel.html#length/1
-[list]: https://hexdocs.pm/elixir/List.html
-[stream]: https://hexdocs.pm/elixir/Stream.html
-[tl]: https://hexdocs.pm/elixir/Kernel.html#tl/1
+[prelude]: https://hackage.haskell.org/package/base/docs/Prelude.html
+[list]: https://hackage.haskell.org/package/base/docs/Data-List.html
+[head]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:head
+[tail]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:tail
+[elem]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:elem
+[length]: https://hackage.haskell.org/package/base/docs/Prelude.html#v:length
 [linked-list-wiki]: https://en.wikipedia.org/wiki/Linked_list

exercises/concept/language-list/.meta/design.md

@@ -25,7 +25,7 @@
   - know of the existence of the `list` type;
   - know of the idea of `list` design;
   - know some basic patterns / functions
-    - like `[]`, `[_:_]`, `head`, `tail`, `length/1`, `elem`
+    - like `[]`, `[_:_]`, `head`, `tail`, `length`, `elem`
 - `string-literals`
   - not a standalone concept, captured in `basics`
   - know how to write out a string with double quotes