wat

README.md

@@ -36,3 +36,4 @@ solution.
   - [Day 5](src/Years/Y2015/Day5.md)
   - [Day 6](src/Years/Y2015/Day6.md)
   - [Day 7](src/Years/Y2015/Day7.md)
+  - [Day 8](src/Years/Y2015/Day8.md)

src/Years/Y2015.md

@@ -14,6 +14,7 @@ import Years.Y2015.Day4
 import Years.Y2015.Day5
 import Years.Y2015.Day6
 import Years.Y2015.Day7
+import Years.Y2015.Day8
 -->
 
 # Days
@@ -66,6 +67,12 @@ y2015 = MkYear 2015 [
   , day7
 ```
 
+## [Day 8](Y2015/Day8.md)
+
+```idris
+  , day8
+```
+
 ```idris
   ]
 ```

src/Years/Y2015/Day8.md

@@ -0,0 +1,176 @@
+# Year 2015 Day 8
+
+<!-- idris
+module Years.Y2015.Day8
+
+import Control.Eff
+
+import Data.Primitives.Interpolation
+
+import Runner
+-->
+
+```idris
+import Data.String
+import Data.Vect
+import Data.Either
+```
+
+## Parsing
+
+Effect alias for a parser
+
+```idris
+Parser : List (Type -> Type)
+Parser =
+  [Choose, State (List Char), Except String]
+```
+
+Get the next character from the state, modifying it in place
+
+```idris
+getNext : Eff Parser Char
+getNext = do
+  chars <- get
+  case chars of 
+    [] => throw "End of Input"
+    (x :: xs) => do
+      put xs
+      pure x
+```
+
+Parse a quote 
+```idris
+quote : Eff Parser ()
+quote = do
+  char <- getNext
+  if char == '"'
+    then pure ()
+    else throw "Expected quote, found: \{show char}"
+```
+
+Parse a char that's not a quote or an escape character
+
+```idris
+normal : Eff Parser Char
+normal = do
+  char <- getNext
+  if any (char ==) (the (List _) ['\\', '"'])
+    then throw "Tried to parse a special character as normal \{show char}"
+    else pure char
+```
+
+Parse a hex digit
+
+```idris
+hexDigit : Eff Parser Int
+hexDigit = do
+  char <- getNext
+  case toLower char of
+    '0' => pure 0x0
+    '1' => pure 0x1
+    '2' => pure 0x2
+    '3' => pure 0x3
+    '4' => pure 0x4
+    '5' => pure 0x5
+    '6' => pure 0x6
+    '7' => pure 0x7
+    '8' => pure 0x8
+    '9' => pure 0x9
+    'a' => pure 0xa
+    'b' => pure 0xb
+    'c' => pure 0xc
+    'd' => pure 0xd
+    'e' => pure 0xe
+    'f' => pure 0xf
+    _ => throw "Invalid hex digit: \{show char}"
+```
+
+Parse an escaped character
+
+```idris
+escaped : Eff Parser Char
+escaped = do 
+  escape <- getNext
+  if escape == '\\'
+    then do
+      first <- getNext
+      case first of
+        '\\' => pure '\\'
+        '"'  => pure '"'
+        'x'  => do
+          [x, y] : Vect _ Int <- sequence [hexDigit, hexDigit]
+          -- Fails to compile 
+          -- pure . chr $ x * 0x10 + y
+          -- Compiles
+          pure . (const 'a') $ x * 0x10 + y
+        _    => throw "Invalid Escape Character: \{show first}"
+    else throw "Tried to parse non escape as escape \{show escape}" 
+```
+
+Parse any non-quote character 
+
+```idris
+character : Eff Parser Char
+character = oneOfM (the (List _) [escaped, normal])
+```
+
+Run a parser until it runs out 
+
+```idris
+parseMany : Eff Parser t -> Eff Parser (List t)
+parseMany x = do
+  Just next <- lift $ catch (\_ => pure Nothing) (map Just x)
+    | _ => pure []
+  map (next ::) (parseMany x)
+```
+
+Parse any number of non-quote characters
+
+```idris
+characters : Eff Parser (List Char)
+characters = parseMany character
+```
+
+Parse a quote delimited string
+
+```idris
+parseString : Eff Parser (List Char)
+parseString = do
+  quote
+  xs <- characters
+  quote
+  pure xs
+```
+
+Run a parser
+
+```idris
+runParser : Eff Parser t -> String -> Maybe t
+runParser m str = 
+  map fst . head' . rights
+  . extract . runChoose {f = List} . runExcept . runState (unpack str) 
+  $ m
+  
+```
+
+## Part Functions
+
+### Part 1
+
+```idris
+part1 : Eff (PartEff String) (Nat, List (List Char, List Char))
+part1 = do
+  inputs <- map (lines . trim) $ askAt "input"
+  let outputs = map (map pack . runParser parseString) inputs
+  let pairs = zip inputs outputs
+  let debug_out = joinBy "\n" . map show $ pairs
+  putStrLn debug_out
+  ?part1_rhs_1
+```
+
+<!-- idris
+public export
+day8 : Day
+day8 = First 8 part1
+-->