Sync docs and metadata (#771)

exercises/practice/accumulate/.meta/config.json

@@ -26,5 +26,5 @@
   },
   "blurb": "Implement the `accumulate` operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.",
   "source": "Conversation with James Edward Gray II",
-  "source_url": "https://twitter.com/jeg2"
+  "source_url": "http://graysoftinc.com/"
 }

exercises/practice/acronym/.docs/instructions.md

@@ -10,8 +10,8 @@ Punctuation is handled as follows: hyphens are word separators (like whitespace)
 
 For example:
 
-|Input|Output|
-|-|-|
-|As Soon As Possible|ASAP|
-|Liquid-crystal display|LCD|
-|Thank George It's Friday!|TGIF|
+| Input                     | Output |
+| ------------------------- | ------ |
+| As Soon As Possible       | ASAP   |
+| Liquid-crystal display    | LCD    |
+| Thank George It's Friday! | TGIF   |

exercises/practice/allergies/.docs/instructions.md

@@ -22,6 +22,6 @@ Now, given just that score of 34, your program should be able to say:
 - Whether Tom is allergic to any one of those allergens listed above.
 - All the allergens Tom is allergic to.
 
-Note: a given score may include allergens **not** listed above (i.e.  allergens that score 256, 512, 1024, etc.).
+Note: a given score may include allergens **not** listed above (i.e. allergens that score 256, 512, 1024, etc.).
 Your program should ignore those components of the score.
 For example, if the allergy score is 257, your program should only report the eggs (1) allergy.

exercises/practice/anagram/.docs/instructions.md

@@ -1,9 +1,9 @@
 # Instructions
 
-An anagram is a rearrangement of letters to form a new word: for example `"owns"` is an anagram of `"snow"`.
-A word is not its own anagram: for example, `"stop"` is not an anagram of `"stop"`.
+Your task is to, given a target word and a set of candidate words, to find the subset of the candidates that are anagrams of the target.
 
-Given a target word and a set of candidate words, this exercise requests the anagram set: the subset of the candidates that are anagrams of the target.
+An anagram is a rearrangement of letters to form a new word: for example `"owns"` is an anagram of `"snow"`.
+A word is _not_ its own anagram: for example, `"stop"` is not an anagram of `"stop"`.
 
 The target and candidates are words of one or more ASCII alphabetic characters (`A`-`Z` and `a`-`z`).
 Lowercase and uppercase characters are equivalent: for example, `"PoTS"` is an anagram of `"sTOp"`, but `StoP` is not an anagram of `sTOp`.

exercises/practice/anagram/.docs/introduction.md

@@ -0,0 +1,12 @@
+# Introduction
+
+At a garage sale, you find a lovely vintage typewriter at a bargain price!
+Excitedly, you rush home, insert a sheet of paper, and start typing away.
+However, your excitement wanes when you examine the output: all words are garbled!
+For example, it prints "stop" instead of "post" and "least" instead of "stale."
+Carefully, you try again, but now it prints "spot" and "slate."
+After some experimentation, you find there is a random delay before each letter is printed, which messes up the order.
+You now understand why they sold it for so little money!
+
+You realize this quirk allows you to generate anagrams, which are words formed by rearranging the letters of another word.
+Pleased with your finding, you spend the rest of the day generating hundreds of anagrams.

exercises/practice/binary-search-tree/.meta/config.json

@@ -20,6 +20,5 @@
     ]
   },
   "blurb": "Insert and search for numbers in a binary tree.",
-  "source": "Josh Cheek",
-  "source_url": "https://twitter.com/josh_cheek"
+  "source": "Josh Cheek"
 }

exercises/practice/binary-search/.docs/instructions.md

@@ -11,7 +11,7 @@ Binary search only works when a list has been sorted.
 
 The algorithm looks like this:
 
-- Find the middle element of a *sorted* list and compare it with the item we're looking for.
+- Find the middle element of a _sorted_ list and compare it with the item we're looking for.
 - If the middle element is our item, then we're done!
 - If the middle element is greater than our item, we can eliminate that element and all the elements **after** it.
 - If the middle element is less than our item, we can eliminate that element and all the elements **before** it.

exercises/practice/bowling/.docs/instructions.md

@@ -23,9 +23,9 @@ There are three cases for the tabulation of a frame.
 
 Here is a three frame example:
 
-| Frame 1         | Frame 2       | Frame 3                |
-| :-------------: |:-------------:| :---------------------:|
-| X (strike)      | 5/ (spare)    | 9 0 (open frame)       |
+|  Frame 1   |  Frame 2   |     Frame 3      |
+| :--------: | :--------: | :--------------: |
+| X (strike) | 5/ (spare) | 9 0 (open frame) |
 
 Frame 1 is (10 + 5 + 5) = 20
 

exercises/practice/circular-buffer/.docs/instructions.md

@@ -4,39 +4,55 @@ A circular buffer, cyclic buffer or ring buffer is a data structure that uses a
 
 A circular buffer first starts empty and of some predefined length.
 For example, this is a 7-element buffer:
-<!-- prettier-ignore -->
-    [ ][ ][ ][ ][ ][ ][ ]
+
+```text
+[ ][ ][ ][ ][ ][ ][ ]
+```
 
 Assume that a 1 is written into the middle of the buffer (exact starting location does not matter in a circular buffer):
-<!-- prettier-ignore -->
-    [ ][ ][ ][1][ ][ ][ ]
+
+```text
+[ ][ ][ ][1][ ][ ][ ]
+```
 
 Then assume that two more elements are added — 2 & 3 — which get appended after the 1:
-<!-- prettier-ignore -->
-    [ ][ ][ ][1][2][3][ ]
+
+```text
+[ ][ ][ ][1][2][3][ ]
+```
 
 If two elements are then removed from the buffer, the oldest values inside the buffer are removed.
 The two elements removed, in this case, are 1 & 2, leaving the buffer with just a 3:
-<!-- prettier-ignore -->
-    [ ][ ][ ][ ][ ][3][ ]
+
+```text
+[ ][ ][ ][ ][ ][3][ ]
+```
 
 If the buffer has 7 elements then it is completely full:
-<!-- prettier-ignore -->
-    [5][6][7][8][9][3][4]
+
+```text
+[5][6][7][8][9][3][4]
+```
 
 When the buffer is full an error will be raised, alerting the client that further writes are blocked until a slot becomes free.
 
 When the buffer is full, the client can opt to overwrite the oldest data with a forced write.
 In this case, two more elements — A & B — are added and they overwrite the 3 & 4:
-<!-- prettier-ignore -->
-    [5][6][7][8][9][A][B]
+
+```text
+[5][6][7][8][9][A][B]
+```
 
 3 & 4 have been replaced by A & B making 5 now the oldest data in the buffer.
 Finally, if two elements are removed then what would be returned is 5 & 6 yielding the buffer:
-<!-- prettier-ignore -->
-    [ ][ ][7][8][9][A][B]
+
+```text
+[ ][ ][7][8][9][A][B]
+```
 
 Because there is space available, if the client again uses overwrite to store C & D then the space where 5 & 6 were stored previously will be used not the location of 7 & 8.
 7 is still the oldest element and the buffer is once again full.
-<!-- prettier-ignore -->
-    [C][D][7][8][9][A][B]
+
+```text
+[C][D][7][8][9][A][B]
+```

exercises/practice/clock/.meta/config.json

@@ -24,6 +24,5 @@
     ]
   },
   "blurb": "Implement a clock that handles times without dates.",
-  "source": "Pairing session with Erin Drummond",
-  "source_url": "https://twitter.com/ebdrummond"
+  "source": "Pairing session with Erin Drummond"
 }

exercises/practice/flatten-array/.docs/instructions.md

@@ -2,7 +2,7 @@
 
 Take a nested list and return a single flattened list with all values except nil/null.
 
-The challenge is to write a function that accepts an arbitrarily-deep nested list-like structure and returns a flattened structure without any nil/null values.
+The challenge is to take an arbitrarily-deep nested list-like structure and produce a flattened structure without any nil/null values.
 
 For example:
 

exercises/practice/hamming/.docs/instructions.md

@@ -1,6 +1,6 @@
 # Instructions
 
-Calculate the Hamming Distance between two DNA strands.
+Calculate the Hamming distance between two DNA strands.
 
 Your body is made up of cells that contain DNA.
 Those cells regularly wear out and need replacing, which they achieve by dividing into daughter cells.
@@ -9,18 +9,18 @@ In fact, the average human body experiences about 10 quadrillion cell divisions
 When cells divide, their DNA replicates too.
 Sometimes during this process mistakes happen and single pieces of DNA get encoded with the incorrect information.
 If we compare two strands of DNA and count the differences between them we can see how many mistakes occurred.
-This is known as the "Hamming Distance".
+This is known as the "Hamming distance".
 
-We read DNA using the letters C,A,G and T.
+We read DNA using the letters C, A, G and T.
 Two strands might look like this:
 
     GAGCCTACTAACGGGAT
     CATCGTAATGACGGCCT
     ^ ^ ^  ^ ^    ^^
 
-They have 7 differences, and therefore the Hamming Distance is 7.
+They have 7 differences, and therefore the Hamming distance is 7.
 
-The Hamming Distance is useful for lots of things in science, not just biology, so it's a nice phrase to be familiar with :)
+The Hamming distance is useful for lots of things in science, not just biology, so it's a nice phrase to be familiar with :)
 
 ## Implementation notes
 

exercises/practice/hello-world/.meta/config.json

@@ -23,7 +23,7 @@
       ".meta/Sources/HelloWorld/HelloWorldExample.swift"
     ]
   },
-  "blurb": "The classical introductory exercise. Just say \"Hello, World!\".",
+  "blurb": "Exercism's classic introductory exercise. Just say \"Hello, World!\".",
   "source": "This is an exercise to introduce users to using Exercism",
   "source_url": "https://en.wikipedia.org/wiki/%22Hello,_world!%22_program"
 }

exercises/practice/isogram/.docs/instructions.md

@@ -11,4 +11,4 @@ Examples of isograms:
 - downstream
 - six-year-old
 
-The word *isograms*, however, is not an isogram, because the s repeats.
+The word _isograms_, however, is not an isogram, because the s repeats.

exercises/practice/list-ops/.docs/instructions.md

@@ -7,11 +7,13 @@ Implement a series of basic list operations, without using existing functions.
 
 The precise number and names of the operations to be implemented will be track dependent to avoid conflicts with existing names, but the general operations you will implement include:
 
-- `append` (*given two lists, add all items in the second list to the end of the first list*);
-- `concatenate` (*given a series of lists, combine all items in all lists into one flattened list*);
-- `filter` (*given a predicate and a list, return the list of all items for which `predicate(item)` is True*);
-- `length` (*given a list, return the total number of items within it*);
-- `map` (*given a function and a list, return the list of the results of applying `function(item)` on all items*);
-- `foldl` (*given a function, a list, and initial accumulator, fold (reduce) each item into the accumulator from the left using `function(accumulator, item)`*);
-- `foldr` (*given a function, a list, and an initial accumulator, fold (reduce) each item into the accumulator from the right using `function(item, accumulator)`*);
-- `reverse` (*given a list, return a list with all the original items, but in reversed order*);
+- `append` (_given two lists, add all items in the second list to the end of the first list_);
+- `concatenate` (_given a series of lists, combine all items in all lists into one flattened list_);
+- `filter` (_given a predicate and a list, return the list of all items for which `predicate(item)` is True_);
+- `length` (_given a list, return the total number of items within it_);
+- `map` (_given a function and a list, return the list of the results of applying `function(item)` on all items_);
+- `foldl` (_given a function, a list, and initial accumulator, fold (reduce) each item into the accumulator from the left_);
+- `foldr` (_given a function, a list, and an initial accumulator, fold (reduce) each item into the accumulator from the right_);
+- `reverse` (_given a list, return a list with all the original items, but in reversed order_).
+
+Note, the ordering in which arguments are passed to the fold functions (`foldl`, `foldr`) is significant.

exercises/practice/luhn/.docs/instructions.md

@@ -22,7 +22,8 @@ The first step of the Luhn algorithm is to double every second digit, starting f
 We will be doubling
 
 ```text
-4_3_ 3_9_ 0_4_ 6_6_
+4539 3195 0343 6467
+↑ ↑  ↑ ↑  ↑ ↑  ↑ ↑  (double these)
 ```
 
 If doubling the number results in a number greater than 9 then subtract 9 from the product.

exercises/practice/matching-brackets/.docs/instructions.md

@@ -1,4 +1,5 @@
 # Instructions
 
 Given a string containing brackets `[]`, braces `{}`, parentheses `()`, or any combination thereof, verify that any and all pairs are matched and nested correctly.
-The string may also contain other characters, which for the purposes of this exercise should be ignored.
+Any other characters should be ignored.
+For example, `"{what is (42)}?"` is balanced and `"[text}"` is not.

exercises/practice/matching-brackets/.docs/introduction.md

@@ -0,0 +1,8 @@
+# Introduction
+
+You're given the opportunity to write software for the Bracketeer™, an ancient but powerful mainframe.
+The software that runs on it is written in a proprietary language.
+Much of its syntax is familiar, but you notice _lots_ of brackets, braces and parentheses.
+Despite the Bracketeer™ being powerful, it lacks flexibility.
+If the source code has any unbalanced brackets, braces or parentheses, the Bracketeer™ crashes and must be rebooted.
+To avoid such a scenario, you start writing code that can verify that brackets, braces, and parentheses are balanced before attempting to run it on the Bracketeer™.

exercises/practice/pascals-triangle/.docs/instructions.md

@@ -1,14 +1,35 @@
 # Instructions
 
-Compute Pascal's triangle up to a given number of rows.
+Your task is to output the first N rows of Pascal's triangle.
 
-In Pascal's Triangle each number is computed by adding the numbers to the right and left of the current position in the previous row.
+[Pascal's triangle][wikipedia] is a triangular array of positive integers.
+
+In Pascal's triangle, the number of values in a row is equal to its row number (which starts at one).
+Therefore, the first row has one value, the second row has two values, and so on.
+
+The first (topmost) row has a single value: `1`.
+Subsequent rows' values are computed by adding the numbers directly to the right and left of the current position in the previous row.
+
+If the previous row does _not_ have a value to the left or right of the current position (which only happens for the leftmost and rightmost positions), treat that position's value as zero (effectively "ignoring" it in the summation).
+
+## Example
+
+Let's look at the first 5 rows of Pascal's Triangle:
 
 ```text
     1
    1 1
   1 2 1
  1 3 3 1
 1 4 6 4 1
-# ... etc
 ```
+
+The topmost row has one value, which is `1`.
+
+The leftmost and rightmost values have only one preceding position to consider, which is the position to its right respectively to its left.
+With the topmost value being `1`, it follows from this that all the leftmost and rightmost values are also `1`.
+
+The other values all have two positions to consider.
+For example, the fifth row's (`1 4 6 4 1`) middle value is `6`, as the values to its left and right in the preceding row are `3` and `3`:
+
+[wikipedia]: https://en.wikipedia.org/wiki/Pascal%27s_triangle

exercises/practice/pascals-triangle/.docs/introduction.md

@@ -0,0 +1,22 @@
+# Introduction
+
+With the weather being great, you're not looking forward to spending an hour in a classroom.
+Annoyed, you enter the class room, where you notice a strangely satisfying triangle shape on the blackboard.
+Whilst waiting for your math teacher to arrive, you can't help but notice some patterns in the triangle: the outer values are all ones, each subsequent row has one more value than its previous row and the triangle is symmetrical.
+Weird!
+
+Not long after you sit down, your teacher enters the room and explains that this triangle is the famous [Pascal's triangle][wikipedia].
+
+Over the next hour, your teacher reveals some amazing things hidden in this triangle:
+
+- It can be used to compute how many ways you can pick K elements from N values.
+- It contains the Fibonacci sequence.
+- If you color odd and even numbers differently, you get a beautiful pattern called the [Sierpiński triangle][wikipedia-sierpinski-triangle].
+
+The teacher implores you and your classmates to lookup other uses, and assures you that there are lots more!
+At that moment, the school bell rings.
+You realize that for the past hour, you were completely absorbed in learning about Pascal's triangle.
+You quickly grab your laptop from your bag and go outside, ready to enjoy both the sunshine _and_ the wonders of Pascal's triangle.
+
+[wikipedia]: https://en.wikipedia.org/wiki/Pascal%27s_triangle
+[wikipedia-sierpinski-triangle]: https://en.wikipedia.org/wiki/Sierpi%C5%84ski_triangle

exercises/practice/perfect-numbers/.docs/instructions.md

@@ -1,24 +1,39 @@
 # Instructions
 
-Determine if a number is perfect, abundant, or deficient based on
-Nicomachus' (60 - 120 CE) classification scheme for positive integers.
-
-The Greek mathematician [Nicomachus][nicomachus] devised a classification scheme for positive integers, identifying each as belonging uniquely to the categories of **perfect**, **abundant**, or **deficient** based on their [aliquot sum][aliquot-sum].
-The aliquot sum is defined as the sum of the factors of a number not including the number itself.
-For example, the aliquot sum of 15 is (1 + 3 + 5) = 9
-
-- **Perfect**: aliquot sum = number
-  - 6 is a perfect number because (1 + 2 + 3) = 6
-  - 28 is a perfect number because (1 + 2 + 4 + 7 + 14) = 28
-- **Abundant**: aliquot sum > number
-  - 12 is an abundant number because (1 + 2 + 3 + 4 + 6) = 16
-  - 24 is an abundant number because (1 + 2 + 3 + 4 + 6 + 8 + 12) = 36
-- **Deficient**: aliquot sum < number
-  - 8 is a deficient number because (1 + 2 + 4) = 7
-  - Prime numbers are deficient
-
-Implement a way to determine whether a given number is **perfect**.
-Depending on your language track, you may also need to implement a way to determine whether a given number is **abundant** or **deficient**.
+Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.
+
+The Greek mathematician [Nicomachus][nicomachus] devised a classification scheme for positive integers, identifying each as belonging uniquely to the categories of [perfect](#perfect), [abundant](#abundant), or [deficient](#deficient) based on their [aliquot sum][aliquot-sum].
+The _aliquot sum_ is defined as the sum of the factors of a number not including the number itself.
+For example, the aliquot sum of `15` is `1 + 3 + 5 = 9`.
+
+## Perfect
+
+A number is perfect when it equals its aliquot sum.
+For example:
+
+- `6` is a perfect number because `1 + 2 + 3 = 6`
+- `28` is a perfect number because `1 + 2 + 4 + 7 + 14 = 28`
+
+## Abundant
+
+A number is abundant when it is less than its aliquot sum.
+For example:
+
+- `12` is an abundant number because `1 + 2 + 3 + 4 + 6 = 16`
+- `24` is an abundant number because `1 + 2 + 3 + 4 + 6 + 8 + 12 = 36`
+
+## Deficient
+
+A number is deficient when it is greater than its aliquot sum.
+For example:
+
+- `8` is a deficient number because `1 + 2 + 4 = 7`
+- Prime numbers are deficient
+
+## Task
+
+Implement a way to determine whether a given number is [perfect](#perfect).
+Depending on your language track, you may also need to implement a way to determine whether a given number is [abundant](#abundant) or [deficient](#deficient).
 
 [nicomachus]: https://en.wikipedia.org/wiki/Nicomachus
 [aliquot-sum]: https://en.wikipedia.org/wiki/Aliquot_sum