--- /dev/null
+import Text.Parsec hiding (State)
+import Text.ParserCombinators.Parsec.Number
+import Control.Applicative ((<$), (<*), (*>), (<*>), liftA)
+import Data.List (partition, union, intersect, tails)
+import Data.Char (isDigit)
+import Control.Monad.State.Lazy
+
+data Location = Literal Int | Register Char deriving (Show)
+data Instruction = Cpy Location Location |
+ Inc Location |
+ Dec Location |
+ Jnz Location Int
+ deriving (Show)
+
+data Machine = Machine { a :: Int
+ , b :: Int
+ , c :: Int
+ , d :: Int
+ , pc :: Int
+ , instructions :: [Instruction]}
+ deriving (Show)
+
+emptyMachine :: Machine
+emptyMachine = Machine {a=0, b=0, c=0, d=0, pc=0, instructions=[]}
+
+main :: IO ()
+main = do
+ text <- readFile "advent12.txt"
+ let instructions = successfulParse $ parseIfile text
+ part1 instructions
+ part2 instructions
+
+
+part1 :: [Instruction] -> IO ()
+part1 instrs =
+ do let m0 = emptyMachine {instructions=instrs}
+ let mf = snd $ runState runMachine m0
+ print (a mf)
+
+part2 :: [Instruction] -> IO ()
+part2 instrs =
+ do let m0 = emptyMachine {instructions=instrs, c=1}
+ let mf = snd $ runState runMachine m0
+ print (a mf)
+
+
+
+runMachine :: State Machine ()
+runMachine =
+ do m <- get
+ if (pc m) >= (length $ instructions m)
+ then return ()
+ else do executeStep
+ runMachine
+
+executeStep :: State Machine ()
+executeStep =
+ do m <- get
+ let i = (instructions m)!!(pc m)
+ put (executeInstruction i m)
+
+executeInstruction :: Instruction -> Machine -> Machine
+executeInstruction (Inc (Register r)) m = m' {pc=pc1}
+ where pc1 = (pc m) + 1
+ v = evaluate m (Register r)
+ m' = writeValue m (Register r) (v+1)
+executeInstruction (Dec (Register r)) m = m' {pc=pc1}
+ where pc1 = (pc m) + 1
+ v = evaluate m (Register r)
+ m' = writeValue m (Register r) (v-1)
+executeInstruction (Cpy s d) m = m' {pc=pc1}
+ where pc1 = (pc m) + 1
+ v = evaluate m s
+ m' = writeValue m d v
+executeInstruction (Jnz s d) m
+ | v == 0 = m {pc=pc1}
+ | otherwise = m {pc=pcj}
+ where pc1 = (pc m) + 1
+ pcj = (pc m) + d
+ v = evaluate m s
+
+
+evaluate :: Machine -> Location -> Int
+evaluate _ (Literal i) = i
+evaluate m (Register r) =
+ case r of
+ 'a' -> (a m)
+ 'b' -> (b m)
+ 'c' -> (c m)
+ 'd' -> (d m)
+
+writeValue :: Machine -> Location -> Int -> Machine
+writeValue m (Literal i) _ = m
+writeValue m (Register r) v =
+ case r of
+ 'a' -> m {a=v}
+ 'b' -> m {b=v}
+ 'c' -> m {c=v}
+ 'd' -> m {d=v}
+
+
+instructionFile = instructionLine `endBy` newline
+-- instructionLine = choice [cpyL, incL, decL, jnzL]
+instructionLine = incL <|> decL <|> cpyL <|> jnzL
+
+incL = incify <$> (string "inc" *> spaces *> (oneOf "abcd"))
+ where incify r = Inc (Register r)
+decL = decify <$> (string "dec" *> spaces *> (oneOf "abcd"))
+ where decify r = Dec (Register r)
+cpyL = cpyify <$> (string "cpy" *> spaces *> ((many1 letter) <|> (many1 digit)))
+ <*> (spaces *> (oneOf "abcd"))
+ where cpyify s r = Cpy (readLocation s) (Register r)
+jnzL = jnzify <$> (string "jnz" *> spaces *> ((many1 letter) <|> (many1 digit)))
+ <*> (spaces *> int)
+ where jnzify r d = Jnz (readLocation r) d
+
+
+readLocation :: String -> Location
+readLocation l
+ | all (isDigit) l = Literal (read l)
+ | otherwise = Register (head l)
+
+
+
+parseIfile :: String -> Either ParseError [Instruction]
+parseIfile input = parse instructionFile "(unknown)" input
+
+parseIline :: String -> Either ParseError Instruction
+parseIline input = parse instructionLine "(unknown)" input
+
+successfulParse :: Either ParseError [a] -> [a]
+successfulParse (Left _) = []
+successfulParse (Right a) = a
\ No newline at end of file
--- /dev/null
+<!DOCTYPE html>
+<html lang="en-us">
+<head>
+<meta charset="utf-8"/>
+<title>Day 12 - Advent of Code 2016</title>
+<!--[if lt IE 9]><script src="/static/html5.js"></script><![endif]-->
+<link href='//fonts.googleapis.com/css?family=Source+Code+Pro:300&subset=latin,latin-ext' rel='stylesheet' type='text/css'>
+<link rel="stylesheet" type="text/css" href="/static/style.css?9"/>
+<link rel="shortcut icon" href="/favicon.ico?2"/>
+</head><!--
+
+
+
+
+Oh, hello! Funny seeing you here.
+
+I appreciate your enthusiasm, but you aren't going to find much down here.
+There certainly aren't clues to any of the puzzles. The best surprises don't
+even appear in the source until you unlock them for real.
+
+Please be careful with automated requests; I'm not Google, and I can only take
+so much traffic. Please be considerate so that everyone gets to play.
+
+If you're curious about how Advent of Code works, it's running on some custom
+Perl code. Other than a few integrations (auth, analytics, ads, social media),
+I built the whole thing myself, including the design, animations, prose, and
+all of the puzzles.
+
+The puzzles probably took the longest; the easiest ones were around 45 minutes
+each, but the harder ones took 2-3 hours, and a few even longer than that. A
+lot of effort went into building this thing - I hope you're enjoying playing it
+as much as I enjoyed making it for you!
+
+If you'd like to hang out, I'm @ericwastl on Twitter.
+
+- Eric Wastl
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
+
+
+
+
+
+
+
+
+
+-->
+<body>
+<header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2016/about">[About]</a></li><li><a href="/2016/support">[AoC++]</a></li><li><a href="/2016/events">[Events]</a></li><li><a href="/2016/settings">[Settings]</a></li><li><a href="/2016/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <span class="supporter">(AoC++)</span> <span class="star-count">24*</span></div></div><div><h1 class="title-event"> <span class="title-event-wrap">//</span><a href="/2016">2016</a><span class="title-event-wrap"></span></h1><nav><ul><li><a href="/2016">[Calendar]</a></li><li><a href="/2016/leaderboard">[Leaderboard]</a></li><li><a href="/2016/stats">[Stats]</a></li><li><a href="/2016/sponsors">[Sponsors]</a></li></ul></nav></div></header>
+
+<div id="sidebar">
+<div id="sponsor"><div class="quiet">Our <a href="/2016/sponsors">sponsors</a> help make AoC possible:</div><p><a href="https://info.esparklearning.com/join-our-team-full-stack-engineer" target="_blank" onclick="if(ga)ga('send','event','sponsor','click',this.href);">eSpark Learning</a> - Solve the greatest puzzle of our day - transform education</p></div>
+<div id="ad">
+<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
+<!-- Advent of Code Wide Skyscraper -->
+<ins class="adsbygoogle"
+ style="display:inline-block;width:160px;height:600px"
+ data-ad-client="ca-pub-9420604735624631"
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+(adsbygoogle = window.adsbygoogle || []).push({});
+</script>
+</div><!--/ad-->
+</div><!--/sidebar-->
+
+<main>
+<article class="day-desc"><h2>--- Day 12: Leonardo's Monorail ---</h2><p>You finally reach the top floor of this building: a garden with a slanted glass ceiling. Looks like there are no more stars to be had.</p>
+<p>While sitting on a nearby bench amidst some <a href="https://www.google.com/search?q=tiger+lilies&tbm=isch">tiger lilies</a>, you manage to decrypt some of the files you extracted from the servers downstairs.</p>
+<p>According to these documents, Easter Bunny HQ isn't just this building - it's a collection of buildings in the nearby area. They're all connected by a local monorail, and there's another building not far from here! Unfortunately, being night, the monorail is currently not operating.</p>
+<p>You remotely connect to the monorail control systems and discover that the boot sequence expects a password. The password-checking logic (your puzzle input) is easy to extract, but the code it uses is strange: it's <span title="Strangely, this assembunny code doesn't seem to be very good at multiplying.">assembunny</span> code designed for the <a href="11">new computer</a> you just assembled. You'll have to execute the code and get the password.</p>
+<p>The assembunny code you've extracted operates on four <a href="https://en.wikipedia.org/wiki/Processor_register">registers</a> (<code>a</code>, <code>b</code>, <code>c</code>, and <code>d</code>) that start at <code>0</code> and can hold any <a href="https://en.wikipedia.org/wiki/Integer">integer</a>. However, it seems to make use of only a few <a href="https://en.wikipedia.org/wiki/Instruction_set">instructions</a>:</p>
+<ul>
+<li><code>cpy x y</code> <em>copies</em> <code>x</code> (either an integer or the <em>value</em> of a register) into register <code>y</code>.</li>
+<li><code>inc x</code> <em>increases</em> the value of register <code>x</code> by one.</li>
+<li><code>dec x</code> <em>decreases</em> the value of register <code>x</code> by one.</li>
+<li><code>jnz x y</code> <em>jumps</em> to an instruction <code>y</code> away (positive means forward; negative means backward), but only if <code>x</code> is <em>not zero</em>.</li>
+</ul>
+<p>The <code>jnz</code> instruction moves relative to itself: an offset of <code>-1</code> would continue at the previous instruction, while an offset of <code>2</code> would <em>skip over</em> the next instruction.</p>
+<p>For example:</p>
+<pre><code>cpy 41 a
+inc a
+inc a
+dec a
+jnz a 2
+dec a
+</code></pre>
+<p>The above code would set register <code>a</code> to <code>41</code>, increase its value by <code>2</code>, decrease its value by <code>1</code>, and then skip the last <code>dec a</code> (because <code>a</code> is not zero, so the <code>jnz a 2</code> skips it), leaving register <code>a</code> at <code>42</code>. When you move past the last instruction, the program halts.</p>
+<p>After executing the assembunny code in your puzzle input, <em>what value is left in register <code>a</code>?</em></p>
+</article>
+<p>Your puzzle answer was <code>318009</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>As you head down the fire escape to the monorail, you notice it didn't start; register <code>c</code> needs to be initialized to the position of the ignition key.</p>
+<p>If you instead <em>initialize register <code>c</code> to be <code>1</code></em>, what value is now left in register <code>a</code>?</p>
+</article>
+<p>Your puzzle answer was <code>9227663</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
+<p>At this point, you should <a href="/2016">return to your advent calendar</a> and try another puzzle.</p>
+<p>If you still want to see it, you can <a href="12/input" target="_blank">get your puzzle input</a>.</p>
+<p>You can also <span class="share">[Share<span class="share-content">on
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+></span>]</span> this puzzle.</p>
+</main>
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