diff --git a/day8.ml b/day8.ml
new file mode 100644
index 0000000..9161b26
--- /dev/null
+++ b/day8.ml
@@ -0,0 +1,63 @@
+(* Common util. Should probably put this in a module or something.. *)
+let get_one_line file =
+  try Some (input_line file) with
+    End_of_file -> None
+
+let get_lines file =
+  let rec input lines =
+    match get_one_line file with
+      Some line -> input (line :: lines)
+    | None -> List.rev lines
+  in input []
+
+let read_file file =
+  let channel = open_in(file) in
+  get_lines channel
+
+(* --- *)
+
+type operation = Nop | Acc | Jmp
+type instruction = { op: operation; arg: int }
+let op_of_string = function | "nop" -> Nop | "acc" -> Acc | "jmp" -> Jmp
+
+let read_instruction = function |
+  op :: arg :: [] -> { op = op_of_string op; arg = int_of_string arg }
+
+let rec walk line_num acc lines_touched instructions =
+  if List.length instructions < line_num + 1 (* at the end of the list *)
+  then string_of_int acc (* success! *)
+  else let { op; arg } = List.nth instructions line_num in (* match on the instruction *)
+    if List.mem line_num lines_touched (* if we've already been on this line *)
+      then raise (Failure (string_of_int acc)) (* raise a Failure of acc *)
+      else match op with (* otherwise match on the op *)
+        | Nop -> walk (line_num + 1) acc (line_num :: lines_touched) instructions
+        | Acc -> walk (line_num + 1) (acc + arg) (line_num :: lines_touched) instructions
+        | Jmp -> walk (line_num + arg) acc (line_num :: lines_touched) instructions
+
+let swap_instruction ins line_num = (* swap the Nop and Jmp at the given line number *)
+  List.mapi (fun i x ->
+     if line_num = i then match x with (* if this is our line *)
+       | { op = Jmp; arg } -> { op = Nop; arg }
+       | { op = Nop; arg } -> { op = Jmp; arg }
+       | a -> a (* if it is any other op, don't change it *)
+     else x (* if it isn't our line number, don't change it *)
+  ) ins
+
+let rec walk_and_fix line_num instructions =
+  let new_instructions = swap_instruction instructions line_num in (* swap nop and jmp *)
+  try walk 0 0 [] new_instructions (* just return the acc this returns, if it doesn't raise *)
+  with Failure acc -> walk_and_fix (line_num + 1) instructions (* Infinite loop detected. recurse! *)
+
+let () =
+  let ins = read_file "day8.txt"
+    |> List.map @@ String.split_on_char ' '
+    |> List.map read_instruction
+  in
+
+  try walk 0 0 [] ins
+    |> Printf.printf "Complete! Wait this shouldn't have completed.. %s";
+  with Failure acc -> (* catch infinite loop *)
+    Printf.printf "Infinite loop detected. Last acc: %s\n" acc;
+
+  walk_and_fix 0 ins
+    |> Printf.printf "Infinite loop fixed! Last acc: %s\n";
diff --git a/day8.txt b/day8.txt
new file mode 100644
index 0000000..11cfbaa
--- /dev/null
+++ b/day8.txt
@@ -0,0 +1,625 @@
+acc +17
+acc +37
+acc -13
+jmp +173
+nop +100
+acc -7
+jmp +447
+nop +283
+acc +41
+acc +32
+jmp +1
+jmp +585
+jmp +1
+acc -5
+nop +71
+acc +49
+acc -18
+jmp +527
+jmp +130
+jmp +253
+acc +11
+acc -11
+jmp +390
+jmp +597
+jmp +1
+acc +6
+acc +0
+jmp +588
+acc -17
+jmp +277
+acc +2
+nop +163
+jmp +558
+acc +38
+jmp +369
+acc +13
+jmp +536
+acc +38
+acc +39
+acc +6
+jmp +84
+acc +11
+nop +517
+acc +48
+acc +47
+jmp +1
+acc +42
+acc +0
+acc +2
+acc +24
+jmp +335
+acc +44
+acc +47
+jmp +446
+nop +42
+nop +74
+acc +45
+jmp +548
+jmp +66
+acc +1
+jmp +212
+acc +18
+jmp +1
+acc +4
+acc -16
+jmp +366
+acc +0
+jmp +398
+acc +45
+jmp +93
+acc +40
+acc +38
+acc +21
+nop +184
+jmp -46
+nop -9
+jmp +53
+acc +46
+acc +36
+jmp +368
+acc +16
+acc +8
+acc -9
+acc -4
+jmp +328
+acc -15
+acc -5
+acc +21
+jmp +435
+acc -5
+acc +36
+jmp +362
+acc +26
+jmp +447
+jmp +1
+jmp +412
+acc +11
+acc +41
+nop -32
+acc +17
+jmp -63
+jmp +1
+nop +393
+jmp +62
+acc +18
+acc +30
+nop +417
+jmp +74
+acc +29
+acc +23
+jmp +455
+jmp +396
+jmp +395
+acc +33
+nop +137
+nop +42
+jmp +57
+jmp +396
+acc +7
+acc +0
+jmp +354
+acc +15
+acc +50
+jmp -12
+jmp +84
+nop +175
+acc +5
+acc -2
+jmp -82
+acc +1
+acc +26
+jmp +288
+nop -113
+nop +366
+acc +45
+jmp +388
+acc +21
+acc +38
+jmp +427
+acc +33
+jmp -94
+nop -118
+nop +411
+jmp +472
+nop +231
+nop +470
+acc +48
+jmp -124
+jmp +1
+acc +5
+acc +37
+acc +42
+jmp +301
+acc -11
+acc -17
+acc +14
+jmp +357
+acc +6
+acc +20
+acc +13
+jmp +361
+jmp -65
+acc +29
+jmp +26
+jmp +329
+acc +32
+acc +32
+acc +17
+jmp -102
+acc -6
+acc +33
+acc +9
+jmp +189
+acc +3
+jmp -128
+jmp -142
+acc +24
+acc -5
+jmp +403
+acc +28
+jmp +310
+acc +34
+acc +4
+acc +33
+acc +18
+jmp +227
+acc -8
+acc -15
+jmp +112
+jmp +54
+acc +21
+acc +23
+acc +20
+jmp +320
+acc +13
+jmp -77
+acc +15
+nop +310
+nop +335
+jmp +232
+acc -3
+nop +50
+acc +41
+jmp +112
+nop -10
+acc +29
+acc +27
+jmp +52
+acc +40
+nop -132
+acc -16
+acc +27
+jmp +309
+acc -8
+nop +147
+acc +20
+acc +46
+jmp +202
+acc +27
+jmp -43
+jmp +1
+acc +33
+acc -13
+jmp +300
+acc +1
+jmp -202
+acc -17
+acc +0
+acc +34
+jmp -5
+nop +335
+acc -16
+acc -17
+jmp -120
+acc -19
+acc -13
+acc +4
+jmp +368
+jmp +21
+acc +39
+acc +39
+acc -18
+jmp -157
+nop +280
+acc +33
+nop -37
+jmp +32
+acc -16
+acc +18
+acc +46
+jmp -121
+acc -19
+jmp +195
+acc +28
+jmp +124
+jmp +331
+jmp -228
+jmp -146
+jmp +85
+jmp +60
+acc +20
+acc -9
+jmp +303
+jmp -122
+jmp +111
+acc +32
+acc +0
+acc +39
+acc +29
+jmp -31
+nop +320
+jmp -63
+jmp +223
+nop -149
+acc -12
+acc -11
+acc +32
+jmp +309
+jmp -13
+acc -19
+jmp -123
+acc +21
+acc +18
+acc +49
+jmp +175
+acc -14
+nop -129
+acc -2
+acc +31
+jmp +79
+acc +23
+acc +50
+acc +39
+acc +7
+jmp -235
+jmp -166
+acc +9
+jmp +293
+acc -11
+jmp +76
+acc +44
+acc +3
+acc +37
+jmp +123
+nop -104
+jmp -157
+acc +14
+acc +10
+acc +28
+jmp +25
+acc +37
+jmp +188
+jmp -49
+acc -11
+jmp -90
+acc -8
+jmp +197
+acc +5
+jmp +115
+acc +44
+jmp -228
+nop -2
+acc +46
+jmp +130
+nop +183
+nop +106
+acc +27
+acc +37
+jmp -309
+acc +28
+acc -4
+acc -12
+acc +38
+jmp +93
+acc +8
+acc +23
+acc -9
+acc +6
+jmp -42
+acc +10
+acc +35
+acc +4
+jmp -231
+acc +19
+acc +7
+acc +23
+acc +11
+jmp -90
+acc +0
+nop +158
+nop -150
+acc +33
+jmp +107
+acc +48
+acc -2
+jmp -104
+acc +6
+nop -57
+nop +172
+acc -11
+jmp -7
+acc +6
+acc +50
+acc -9
+acc +12
+jmp -171
+acc +3
+jmp +26
+acc +42
+acc +31
+acc +20
+acc +32
+jmp -48
+acc +13
+jmp -6
+jmp +178
+acc +47
+jmp -153
+acc +28
+nop +74
+jmp -162
+acc -15
+nop -104
+acc -9
+jmp -227
+acc +49
+acc -19
+acc +41
+jmp -318
+acc +9
+acc +12
+acc +7
+jmp +34
+jmp +137
+nop -143
+acc -8
+acc +5
+acc +31
+jmp -20
+jmp -237
+acc +39
+acc +0
+jmp -298
+acc +45
+acc -19
+acc +11
+jmp -151
+acc +40
+acc +27
+nop +150
+nop -391
+jmp -341
+acc +1
+acc +11
+acc +18
+nop -234
+jmp +77
+nop +104
+jmp -65
+acc +32
+jmp -27
+nop -317
+nop +159
+acc +14
+acc -10
+jmp -348
+acc +29
+jmp +32
+acc +48
+acc -19
+jmp +17
+jmp -201
+jmp -224
+nop +26
+acc -7
+acc +23
+acc +46
+jmp -6
+acc +22
+acc +39
+acc +9
+acc +23
+jmp -30
+jmp -243
+acc +47
+acc -15
+jmp -298
+jmp -393
+jmp +1
+acc +3
+nop -24
+acc +7
+jmp -59
+acc -6
+acc +26
+jmp -102
+acc +34
+acc +24
+jmp -207
+acc +36
+acc +40
+acc +41
+jmp +1
+jmp -306
+jmp +57
+jmp +1
+nop +99
+acc +28
+jmp -391
+acc +50
+jmp -359
+acc -5
+jmp +9
+jmp -355
+acc +5
+acc +2
+jmp -77
+acc +40
+acc +28
+acc +22
+jmp -262
+nop -287
+acc +34
+acc -4
+nop +112
+jmp -195
+acc +29
+nop -94
+nop -418
+jmp +24
+jmp -190
+acc +2
+jmp -311
+jmp -178
+jmp -276
+acc -12
+acc -18
+jmp +62
+jmp -174
+nop +31
+acc +33
+nop -158
+jmp -417
+acc +3
+acc +21
+acc +47
+jmp +87
+acc +45
+jmp -77
+acc +6
+acc -10
+jmp +1
+jmp -240
+acc +7
+acc +47
+jmp -379
+acc -14
+acc +50
+nop -75
+acc +30
+jmp +70
+jmp -392
+jmp -430
+acc +22
+acc -2
+jmp -492
+jmp +1
+acc -6
+acc +38
+jmp -36
+nop -336
+jmp -32
+jmp +61
+acc +20
+acc -9
+acc +2
+jmp -175
+acc +21
+acc -2
+jmp -6
+jmp -527
+acc +11
+acc +16
+jmp -262
+jmp +1
+nop -327
+acc +29
+jmp -114
+acc +11
+acc +17
+acc +26
+nop -104
+jmp -428
+nop -178
+nop -242
+acc +29
+acc +5
+jmp -245
+jmp -417
+jmp -278
+acc +35
+acc +21
+jmp +1
+nop -263
+jmp +8
+acc +42
+jmp -95
+nop -312
+acc -11
+acc +34
+acc +0
+jmp +19
+acc +8
+acc -13
+acc +32
+acc +21
+jmp -208
+acc +15
+acc +39
+nop -194
+jmp -280
+jmp +24
+nop -516
+acc +21
+acc +48
+jmp -367
+jmp -121
+acc +49
+acc -16
+jmp -136
+acc +0
+jmp -148
+jmp -85
+jmp -103
+nop -446
+jmp -242
+acc -12
+acc +13
+acc +31
+acc -1
+jmp -435
+nop -420
+acc +22
+acc -5
+jmp -567
+nop -354
+acc +11
+acc +33
+acc +45
+jmp -76
+acc -2
+acc +0
+acc +25
+acc +46
+jmp -555
+acc +0
+acc +11
+nop -2
+jmp -394
+jmp -395
+acc +8
+acc +14
+acc +47
+acc +22
+jmp +1