Reformat markdown

src/Years/Y2015/Day3.md

@@ -1,6 +1,7 @@
 # Year 2015 Day 3
 
-This day provides a gentle introduction to `mutual` blocks and mutually recursive functions. 
+This day provides a gentle introduction to `mutual` blocks and mutually
+recursive functions.
 
 <!-- idris
 module Years.Y2015.Day3
@@ -23,13 +24,16 @@ import Util
 
 ## Parsing and data structures
 
-We'll do parsing a little more properly this time, turning the input into a list of movement commands
+We'll do parsing a little more properly this time, turning the input into a list
+of movement commands
 
 ```idris
 data Movement = North | East | South | West
 ```
 
-We need an effectful operation to parse a single char into a movement. We'll pattern match on the char, and include a catch-all case that throws an error in the event of an invalid char
+We need an effectful operation to parse a single char into a movement. We'll
+pattern match on the char, and include a catch-all case that throws an error in
+the event of an invalid char
 
 ```idris
 parseMovement : Has (Except String) fs => (x : Char) -> Eff fs Movement
@@ -40,7 +44,9 @@ parseMovement '<' = pure West
 parseMovement x = throw "Invalid Movement: \{show x}"
 ```
 
-We also need to be able to translate a `Movement` into a vector of length one pointing in the given direction in coordinate space. Somewhat arbitrarily, we chose 'North' to be positive x and 'East' to be positive y.
+We also need to be able to translate a `Movement` into a vector of length one
+pointing in the given direction in coordinate space. Somewhat arbitrarily, we
+chose 'North' to be positive x and 'East' to be positive y.
 
 ```idris
 vector : Movement -> (Integer, Integer)
@@ -54,11 +60,17 @@ vector West = (0, -1)
 
 ### Visited houses
 
-This is a pretty simple task, we are just applying the movements to our current position, and adding our current position to the set of visited locations, so we'll handle this with a normal tail recursive function.
+This is a pretty simple task, we are just applying the movements to our current
+position, and adding our current position to the set of visited locations, so
+we'll handle this with a normal tail recursive function.
 
-To keep the api nice, we wont ask for the set or the starting location in the top-level function, and instead have the top level function initialize the set and location before passing control to the inner tail-recursive variant.
+To keep the api nice, we wont ask for the set or the starting location in the
+top-level function, and instead have the top level function initialize the set
+and location before passing control to the inner tail-recursive variant.
 
-Because the starting location gets a present, we'll add our location to the set before performing the movement, so we will need to add our final location to the set in the recursive base case.
+Because the starting location gets a present, we'll add our location to the set
+before performing the movement, so we will need to add our final location to the
+set in the recursive base case.
 
 ```idris
 visitedLocations : List Movement -> SortedSet (Integer, Integer)
@@ -73,13 +85,26 @@ visitedLocations xs = visitor xs empty (0, 0)
 
 ### Robo Santa
 
-This one gets a bit more interesting, we'll adopt the same tail recursive approach, but instead use a `mutual` block and two mutually recursive functions to handle the alternation between santa and robo santa. The `visitSanta` function will pass control to `visitRobo` after executing its movement, and vise versa.
+This one gets a bit more interesting, we'll adopt the same tail recursive
+approach, but instead use a `mutual` block and two mutually recursive functions
+to handle the alternation between santa and robo santa. The `visitSanta`
+function will pass control to `visitRobo` after executing its movement, and vise
+versa.
 
-We'll want to insert both present deliverer's locations in the recursive base case, this may result in a duplicate location, but that's okay because `SortedSet` will only hold at most one of each item inserted into it.
+We'll want to insert both present deliverer's locations in the recursive base
+case, this may result in a duplicate location, but that's okay because
+`SortedSet` will only hold at most one of each item inserted into it.
 
-In idris, there is a general requirement that values be defined before their use, a common feature of dependently typed languages, resulting from the fact that just having the type signature of a function/value alone is not always enough to perform type checking, as functions can appear as part of types, requiring evaluation of the function and making automatic dependency analysis effectively impossible.
+In idris, there is a general requirement that values be defined before their
+use, a common feature of dependently typed languages, resulting from the fact
+that just having the type signature of a function/value alone is not always
+enough to perform type checking, as functions can appear as part of types,
+requiring evaluation of the function and making automatic dependency analysis
+effectively impossible.
 
-Inside a `mutual` block, elaboration behaves differently, elaborating types first and then values in separate passes. This restricts what you can do a little, but enables mutually recursive functions.
+Inside a `mutual` block, elaboration behaves differently, elaborating types
+first and then values in separate passes. This restricts what you can do a
+little, but enables mutually recursive functions.
 
 ```idris
 visitedLocations' : List Movement -> SortedSet (Integer, Integer)
@@ -103,7 +128,9 @@ visitedLocations' xs = visitSanta xs empty (0, 0) (0, 0)
 
 ### Part 1
 
-Similar to the previous day, we get our input, unpack it, and traverse our effectful movement parsing function over it, before feeding that into our solving function.
+Similar to the previous day, we get our input, unpack it, and traverse our
+effectful movement parsing function over it, before feeding that into our
+solving function.
 
 ```idris
 part1 : Eff (PartEff String) (Nat, List Movement)