Add micro-blog (#269)

Author: keiravillekode

config.json

@@ -336,6 +336,14 @@
           "error_handling"
         ]
       },
+      {
+        "slug": "micro-blog",
+        "name": "Micro Blog",
+        "uuid": "8d36d22e-f33f-4753-9d10-486159a256ab",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "resistor-color",
         "name": "Resistor Color",

exercises/practice/micro-blog/.docs/instructions.md

@@ -0,0 +1,37 @@
+# Instructions
+
+You have identified a gap in the social media market for very very short posts.
+Now that Twitter allows 280 character posts, people wanting quick social media updates aren't being served.
+You decide to create your own social media network.
+
+To make your product noteworthy, you make it extreme and only allow posts of 5 or less characters.
+Any posts of more than 5 characters should be truncated to 5.
+
+To allow your users to express themselves fully, you allow Emoji and other Unicode.
+
+The task is to truncate input strings to 5 characters.
+
+## Text Encodings
+
+Text stored digitally has to be converted to a series of bytes.
+There are 3 ways to map characters to bytes in common use.
+
+- **ASCII** can encode English language characters.
+  All characters are precisely 1 byte long.
+- **UTF-8** is a Unicode text encoding.
+  Characters take between 1 and 4 bytes.
+- **UTF-16** is a Unicode text encoding.
+  Characters are either 2 or 4 bytes long.
+
+UTF-8 and UTF-16 are both Unicode encodings which means they're capable of representing a massive range of characters including:
+
+- Text in most of the world's languages and scripts
+- Historic text
+- Emoji
+
+UTF-8 and UTF-16 are both variable length encodings, which means that different characters take up different amounts of space.
+
+Consider the letter 'a' and the emoji '😛'.
+In UTF-16 the letter takes 2 bytes but the emoji takes 4 bytes.
+
+The trick to this exercise is to use APIs designed around Unicode characters (codepoints) instead of Unicode codeunits.

exercises/practice/micro-blog/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "source/micro_blog.d"
+    ],
+    "test": [
+      "source/micro_blog.d"
+    ],
+    "example": [
+      "example/micro_blog.d"
+    ]
+  },
+  "blurb": "Given an input string, truncate it to 5 characters."
+}

exercises/practice/micro-blog/.meta/tests.toml

@@ -0,0 +1,46 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[b927b57f-7c98-42fd-8f33-fae091dc1efc]
+description = "English language short"
+
+[a3fcdc5b-0ed4-4f49-80f5-b1a293eac2a0]
+description = "English language long"
+
+[01910864-8e15-4007-9c7c-ac956c686e60]
+description = "German language short (broth)"
+
+[f263e488-aefb-478f-a671-b6ba99722543]
+description = "German language long (bear carpet → beards)"
+
+[0916e8f1-41d7-4402-a110-b08aa000342c]
+description = "Bulgarian language short (good)"
+
+[bed6b89c-03df-4154-98e6-a61a74f61b7d]
+description = "Greek language short (health)"
+
+[485a6a70-2edb-424d-b999-5529dbc8e002]
+description = "Maths short"
+
+[8b4b7b51-8f48-4fbe-964e-6e4e6438be28]
+description = "Maths long"
+
+[71f4a192-0566-4402-a512-fe12878be523]
+description = "English and emoji short"
+
+[6f0f71f3-9806-4759-a844-fa182f7bc203]
+description = "Emoji short"
+
+[ce71fb92-5214-46d0-a7f8-d5ba56b4cc6e]
+description = "Emoji long"
+
+[5dee98d2-d56e-468a-a1f2-121c3f7c5a0b]
+description = "Royal Flush?"

exercises/practice/micro-blog/dub.sdl

@@ -0,0 +1,2 @@
+name "micro-blog"
+buildRequirements "disallowDeprecations"

exercises/practice/micro-blog/example/micro_blog.d

@@ -0,0 +1,10 @@
+module micro_blog;
+
+import std.algorithm : min;
+import std.conv : to;
+
+pure string truncate(immutable string phrase)
+{
+    dstring str = phrase.to!dstring;
+    return str[0..min(5, str.length)].to!string;
+}

exercises/practice/micro-blog/source/micro_blog.d

@@ -0,0 +1,50 @@
+module micro_blog;
+
+pure string truncate(immutable string phrase)
+{
+    // implement this function
+}
+
+unittest
+{
+    immutable int allTestsEnabled = 0;
+
+    // English language short
+    assert(truncate("Hi") == "Hi");
+
+    static if (allTestsEnabled)
+    {
+        // English language long
+        assert(truncate("Hello there") == "Hello");
+
+        // German language short (broth)
+        assert(truncate("brühe") == "brühe");
+
+        // German language long (bear carpet → beards)
+        assert(truncate("Bärteppich") == "Bärte");
+
+        // Bulgarian language short (good)
+        assert(truncate("Добър") == "Добър");
+
+        // Greek language short (health)
+        assert(truncate("υγειά") == "υγειά");
+
+        // Maths short
+        assert(truncate("a=πr²") == "a=πr²");
+
+        // Maths long
+        assert(truncate("∅⊊ℕ⊊ℤ⊊ℚ⊊ℝ⊊ℂ") == "∅⊊ℕ⊊ℤ");
+
+        // English and emoji short
+        assert(truncate("Fly 🛫") == "Fly 🛫");
+
+        // Emoji short
+        assert(truncate("💇") == "💇");
+
+        // Emoji long
+        assert(truncate("❄🌡🤧🤒🏥🕰😀") == "❄🌡🤧🤒🏥");
+
+        // Royal Flush?
+        assert(truncate("🃎🂸🃅🃋🃍🃁🃊") == "🃎🂸🃅🃋🃍");
+    }
+}