Sync docs and metadata

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

@@ -29,5 +29,5 @@
   },
   "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/affine-cipher/.docs/instructions.md

@@ -18,10 +18,10 @@ E(x) = (ai + b) mod m
 
 Where:
 
-- `i` is the letter's index from `0` to the length of the alphabet - 1
+- `i` is the letter's index from `0` to the length of the alphabet - 1.
 - `m` is the length of the alphabet.
   For the Roman alphabet `m` is `26`.
-- `a` and `b` are integers which make the encryption key
+- `a` and `b` are integers which make up the encryption key.
 
 Values `a` and `m` must be _coprime_ (or, _relatively prime_) for automatic decryption to succeed, i.e., they have number `1` as their only common factor (more information can be found in the [Wikipedia article about coprime integers][coprime-integers]).
 In case `a` is not coprime to `m`, your program should indicate that this is an error.

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/alphametics/.docs/instructions.md

@@ -1,6 +1,6 @@
 # Instructions
 
-Write a function to solve alphametics puzzles.
+Given an alphametics puzzle, find the correct solution.
 
 [Alphametics][alphametics] is a puzzle where letters in words are replaced with numbers.
 
@@ -26,6 +26,4 @@ This is correct because every letter is replaced by a different number and the w
 
 Each letter must represent a different digit, and the leading digit of a multi-digit number must not be zero.
 
-Write a function to solve alphametics puzzles.
-
 [alphametics]: https://en.wikipedia.org/wiki/Alphametics

exercises/practice/alphametics/.meta/config.json

@@ -26,5 +26,5 @@
       "stack.yaml"
     ]
   },
-  "blurb": "Write a function to solve alphametics puzzles."
+  "blurb": "Given an alphametics puzzle, find the correct solution."
 }

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

@@ -5,9 +5,9 @@ An [Armstrong number][armstrong-number] is a number that is the sum of its own d
 For example:
 
 - 9 is an Armstrong number, because `9 = 9^1 = 9`
-- 10 is *not* an Armstrong number, because `10 != 1^2 + 0^2 = 1`
+- 10 is _not_ an Armstrong number, because `10 != 1^2 + 0^2 = 1`
 - 153 is an Armstrong number, because: `153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153`
-- 154 is *not* an Armstrong number, because: `154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190`
+- 154 is _not_ an Armstrong number, because: `154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190`
 
 Write some code to determine whether a number is an Armstrong number.
 

exercises/practice/bank-account/.docs/instructions.md

@@ -3,7 +3,7 @@
 Your task is to implement bank accounts supporting opening/closing, withdrawals, and deposits of money.
 
 As bank accounts can be accessed in many different ways (internet, mobile phones, automatic charges), your bank software must allow accounts to be safely accessed from multiple threads/processes (terminology depends on your programming language) in parallel.
-For example, there may be many deposits and withdrawals occurring in parallel; you need to ensure there is no [race conditions][wikipedia] between when you read the account balance and set the new balance.
+For example, there may be many deposits and withdrawals occurring in parallel; you need to ensure there are no [race conditions][wikipedia] between when you read the account balance and set the new balance.
 
 It should be possible to close an account; operations against a closed account must fail.
 

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

@@ -29,6 +29,5 @@
     ]
   },
   "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/clock/.meta/config.json

@@ -32,6 +32,5 @@
     ]
   },
   "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/darts/.docs/instructions.md

@@ -1,6 +1,6 @@
 # Instructions
 
-Write a function that returns the earned points in a single toss of a Darts game.
+Calculate the points scored in a single toss of a Darts game.
 
 [Darts][darts] is a game where players throw darts at a [target][darts-target].
 
@@ -16,7 +16,7 @@ In our particular instance of the game, the target rewards 4 different amounts o
 The outer circle has a radius of 10 units (this is equivalent to the total radius for the entire target), the middle circle a radius of 5 units, and the inner circle a radius of 1.
 Of course, they are all centered at the same point — that is, the circles are [concentric][] defined by the coordinates (0, 0).
 
-Write a function that given a point in the target (defined by its [Cartesian coordinates][cartesian-coordinates] `x` and `y`, where `x` and `y` are [real][real-numbers]), returns the correct amount earned by a dart landing at that point.
+Given a point in the target (defined by its [Cartesian coordinates][cartesian-coordinates] `x` and `y`, where `x` and `y` are [real][real-numbers]), calculate the correct score earned by a dart landing at that point.
 
 ## Credit
 

exercises/practice/darts/.meta/config.json

@@ -17,6 +17,6 @@
       "stack.yaml"
     ]
   },
-  "blurb": "Write a function that returns the earned points in a single toss of a Darts game.",
+  "blurb": "Calculate the points scored in a single toss of a Darts game.",
   "source": "Inspired by an exercise created by a professor Della Paolera in Argentina"
 }

exercises/practice/go-counting/.docs/instructions.md

@@ -5,10 +5,10 @@ Count the scored points on a Go board.
 In the game of go (also known as baduk, igo, cờ vây and wéiqí) points are gained by completely encircling empty intersections with your stones.
 The encircled intersections of a player are known as its territory.
 
-Write a function that determines the territory of each player.
+Calculate the territory of each player.
 You may assume that any stones that have been stranded in enemy territory have already been taken off the board.
 
-Write a function that determines the territory which includes a specified coordinate.
+Determine the territory which includes a specified coordinate.
 
 Multiple empty intersections may be encircled at once and for encircling only horizontal and vertical neighbors count.
 In the following diagram the stones which matter are marked "O" and the stones that don't are marked "I" (ignored).
@@ -25,7 +25,7 @@ Empty spaces represent empty intersections.
 
 To be more precise an empty intersection is part of a player's territory if all of its neighbors are either stones of that player or empty intersections that are part of that player's territory.
 
-For more information see [wikipedia][go-wikipedia] or [Sensei's Library][go-sensei].
+For more information see [Wikipedia][go-wikipedia] or [Sensei's Library][go-sensei].
 
 [go-wikipedia]: https://en.wikipedia.org/wiki/Go_%28game%29
 [go-sensei]: https://senseis.xmp.net/

exercises/practice/grade-school/.docs/instructions.md

@@ -1,7 +1,6 @@
 # Instructions
 
-Given students' names along with the grade that they are in, create a roster
-for the school.
+Given students' names along with the grade that they are in, create a roster for the school.
 
 In the end, you should be able to:
 
@@ -11,28 +10,12 @@ In the end, you should be able to:
 - Get a list of all students enrolled in a grade
   - "Which students are in grade 2?"
   - "We've only got Jim just now."
-- Get a sorted list of all students in all grades.  Grades should sort
-  as 1, 2, 3, etc., and students within a grade should be sorted
-  alphabetically by name.
+- Get a sorted list of all students in all grades.
+  Grades should sort as 1, 2, 3, etc., and students within a grade should be sorted alphabetically by name.
   - "Who all is enrolled in school right now?"
-  - "Let me think. We have
-  Anna, Barb, and Charlie in grade 1,
-  Alex, Peter, and Zoe in grade 2
-  and Jim in grade 5.
-  So the answer is: Anna, Barb, Charlie, Alex, Peter, Zoe and Jim"
+  - "Let me think.
+    We have Anna, Barb, and Charlie in grade 1, Alex, Peter, and Zoe in grade 2 and Jim in grade 5.
+    So the answer is: Anna, Barb, Charlie, Alex, Peter, Zoe and Jim"
 
-Note that all our students only have one name.  (It's a small town, what
-do you want?)
-
-## For bonus points
-
-Did you get the tests passing and the code clean? If you want to, these
-are some additional things you could try:
-
-- If you're working in a language with mutable data structures and your
-  implementation allows outside code to mutate the school's internal DB
-  directly, see if you can prevent this. Feel free to introduce additional
-  tests.
-
-Then please share your thoughts in a comment on the submission. Did this
-experiment make the code better? Worse? Did you learn anything from it?
+Note that all our students only have one name (It's a small town, what do you want?) and each student cannot be added more than once to a grade or the roster.
+In fact, when a test attempts to add the same student more than once, your implementation should indicate that this is incorrect.

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/hamming/.meta/config.json

@@ -28,7 +28,7 @@
       "stack.yaml"
     ]
   },
-  "blurb": "Calculate the Hamming difference between two DNA strands.",
+  "blurb": "Calculate the Hamming distance between two DNA strands.",
   "source": "The Calculating Point Mutations problem at Rosalind",
   "source_url": "https://rosalind.info/problems/hamm/"
 }

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

@@ -26,7 +26,7 @@
       "stack.yaml"
     ]
   },
-  "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

@@ -7,13 +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*);
-- `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*).
+- `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/parallel-letter-frequency/.docs/instructions.md

@@ -4,4 +4,4 @@ Count the frequency of letters in texts using parallel computation.
 
 Parallelism is about doing things in parallel that can also be done sequentially.
 A common example is counting the frequency of letters.
-Create a function that returns the total frequency of each letter in a list of texts and that employs parallelism.
+Employ parallelism to calculate the total frequency of each letter in a list of texts.

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