Add micro-blog exercise

config.json

@@ -329,6 +329,14 @@
         "prerequisites": [],
         "difficulty": 4
       },
+      {
+        "slug": "micro-blog",
+        "name": "Micro Blog",
+        "uuid": "5ec317e6-1d7e-4253-9aa2-de310588bdaa",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "slug": "perfect-numbers",
         "name": "Perfect Numbers",

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": [
+      "micro_blog.fut"
+    ],
+    "test": [
+      "test.fut"
+    ],
+    "example": [
+      ".meta/example.fut"
+    ]
+  },
+  "blurb": "Given an input string, truncate it to 5 characters."
+}

exercises/practice/micro-blog/.meta/example.fut

@@ -0,0 +1,5 @@
+def truncate (phrase: *[]u8): *[]u8 =
+  let (index, count) = loop (index, count) = (0, 0) while index < (length phrase) && count < 6 do
+    if (phrase[index] & 0xc0) == 0x80 then (index + 1, count) else (index + 1, count + 1)
+  in
+    if count == 6 then phrase[0:index - 1] else phrase

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/micro_blog.fut

@@ -0,0 +1 @@
+def truncate (phrase: *[]u8): *[]u8 = ???

exercises/practice/micro-blog/test.fut

@@ -0,0 +1,64 @@
+import "micro_blog"
+
+-- English language short
+-- ==
+-- input { "Hi" }
+-- output { "Hi" }
+
+-- English language long
+-- ==
+-- input { "Hello there" }
+-- output { "Hello" }
+
+-- German language short (broth)
+-- ==
+-- input { "brühe" }
+-- output { "brühe" }
+
+-- German language long (bear carpet → beards)
+-- ==
+-- input { "Bärteppich" }
+-- output { "Bärte" }
+
+-- Bulgarian language short (good)
+-- ==
+-- input { "Добър" }
+-- output { "Добър" }
+
+-- Greek language short (health)
+-- ==
+-- input { "υγειά" }
+-- output { "υγειά" }
+
+-- Maths short
+-- ==
+-- input { "a=πr²" }
+-- output { "a=πr²" }
+
+-- Maths long
+-- ==
+-- input { "∅⊊ℕ⊊ℤ⊊ℚ⊊ℝ⊊ℂ" }
+-- output { "∅⊊ℕ⊊ℤ" }
+
+-- English and emoji short
+-- ==
+-- input { "Fly 🛫" }
+-- output { "Fly 🛫" }
+
+-- Emoji short
+-- ==
+-- input { "💇" }
+-- output { "💇" }
+
+-- Emoji long
+-- ==
+-- input { "❄🌡🤧🤒🏥🕰😀" }
+-- output { "❄🌡🤧🤒🏥" }
+
+-- Royal Flush?
+-- ==
+-- input { "🃎🂸🃅🃋🃍🃁🃊" }
+-- output { "🃎🂸🃅🃋🃍" }
+
+let main (phrase: *[]u8): *[]u8 =
+  truncate phrase

generators/exercises/micro_blog.py

@@ -0,0 +1,11 @@
+def gen_test_case(prop, description, inp, expected, f):
+    phrase = inp["phrase"]
+    f.write(f"-- {description}\n")
+    f.write("-- ==\n")
+    f.write(f'-- input {{ "{phrase}" }}\n')
+    f.write(f'-- output {{ "{expected}" }}\n\n')
+
+
+def gen_main(f):
+    f.write("let main (phrase: *[]u8): *[]u8 =\n")
+    f.write("  truncate phrase\n")