diff --git a/lib/util/list.ml b/lib/util/list.ml
index e1b2404..b1c5c30 100644
--- a/lib/util/list.ml
+++ b/lib/util/list.ml
@@ -1,3 +1,11 @@
+module Syntax = struct
+  let ( let* ) t f = Core.List.bind t ~f
+  let ( and* ) = Core.List.Let_syntax.Let_syntax.both
+  let ( let+ ) t f = Core.List.map t ~f
+  let ( and+ ) = Core.List.Let_syntax.Let_syntax.both
+  let return = Core.List.return
+end
+
 let max_int l = Core.List.max_elt ~compare l |> Option.value_exn
 let min_int l = Core.List.min_elt ~compare l |> Option.value_exn
 let replicate a ~n = Core.List.init n ~f:(const a)
diff --git a/lib/util/parser.ml b/lib/util/parser.ml
index 498d428..844de49 100644
--- a/lib/util/parser.ml
+++ b/lib/util/parser.ml
@@ -7,6 +7,7 @@ module Syntax = struct
     ( >>= ), ( >>| ), ( *> ), ( <* ), ( <|> ), ( <?> ), ( <$> )
   ;;
 
+  let ( let* ), ( let+ ), ( and+ ) = ( let* ), ( let+ ), ( and+ )
   let ( $> ) p a = p >>| const a
   let ( <$ ) a p = p >>| const a
 end
diff --git a/lib/util/sequence.ml b/lib/util/sequence.ml
index c9a3034..85bf433 100644
--- a/lib/util/sequence.ml
+++ b/lib/util/sequence.ml
@@ -1,3 +1,11 @@
+module Syntax = struct
+  let ( let* ) t f = Core.Sequence.bind t ~f
+  let ( and* ) = Core.Sequence.Let_syntax.Let_syntax.both
+  let ( let+ ) t f = Core.Sequence.map t ~f
+  let ( and+ ) = Core.Sequence.Let_syntax.Let_syntax.both
+  let return = Core.Sequence.Let_syntax.Let_syntax.return
+end
+
 let nats = Core.Sequence.unfold ~init:0 ~f:(fun i -> Some (i, i + 1))
 
 let fold_result_exn s ~init ~f =
diff --git a/lib/year2022/day04.ml b/lib/year2022/day04.ml
index c7deaed..ac2f2f1 100644
--- a/lib/year2022/day04.ml
+++ b/lib/year2022/day04.ml
@@ -7,14 +7,14 @@ type range =
   }
 
 let range_p =
-  let%map start = P.integer <* P.char '-'
-  and stop = P.integer in
+  let+ start = P.integer <* P.char '-'
+  and+ stop = P.integer in
   { start; stop }
 ;;
 
 let range_pair_p =
-  let%map a = range_p <* P.char ','
-  and b = range_p in
+  let+ a = range_p <* P.char ','
+  and+ b = range_p in
   a, b
 ;;
 
diff --git a/lib/year2022/day05.ml b/lib/year2022/day05.ml
index 5d12dd6..8dce846 100644
--- a/lib/year2022/day05.ml
+++ b/lib/year2022/day05.ml
@@ -23,9 +23,9 @@ let crate_line_p = P.sep_by1 (P.char ' ') crate_p
 let crate_lines_p = P.sep_by1 P.end_of_line crate_line_p <* P.end_of_line
 
 let move_p =
-  let%map n = P.string "move " *> P.integer
-  and from = P.string " from " *> P.integer
-  and to' = P.string " to " *> P.integer in
+  let+ n = P.string "move " *> P.integer
+  and+ from = P.string " from " *> P.integer
+  and+ to' = P.string " to " *> P.integer in
   { n; from; to' }
 ;;
 
@@ -48,8 +48,8 @@ let to_stacks crates =
 ;;
 
 let instructions_p =
-  let%map crate_lines = crate_lines_p <* drop_line_p <* drop_line_p
-  and moves = moves_p in
+  let+ crate_lines = crate_lines_p <* drop_line_p <* drop_line_p
+  and+ moves = moves_p in
   let crates = to_stacks crate_lines in
   { moves; crates }
 ;;
diff --git a/lib/year2022/day07.ml b/lib/year2022/day07.ml
index f263b2c..eba9503 100644
--- a/lib/year2022/day07.ml
+++ b/lib/year2022/day07.ml
@@ -18,20 +18,20 @@ let name_p =
 ;;
 
 let cd_p =
-  let%map dir = P.string "$ cd " *> name_p in
+  let+ dir = P.string "$ cd " *> name_p in
   Cd dir
 ;;
 
 let ls_p = Ls <$ P.string "$ ls"
 
 let dir_item_p =
-  let%map dir = P.string "dir " *> name_p in
+  let+ dir = P.string "dir " *> name_p in
   DirItem dir
 ;;
 
 let file_item_p =
-  let%map size = P.integer <* P.char ' '
-  and file = name_p in
+  let+ size = P.integer <* P.char ' '
+  and+ file = name_p in
   FileItem (size, file)
 ;;
 
diff --git a/lib/year2022/day08.ml b/lib/year2022/day08.ml
index 12b345f..c987762 100644
--- a/lib/year2022/day08.ml
+++ b/lib/year2022/day08.ml
@@ -16,10 +16,11 @@ let grid_size grid =
 ;;
 
 let coords grid =
+  let open Util.List.Syntax in
   let max_x, max_y = grid_size grid in
-  let%bind.List x = List.range 0 max_x
-  and y = List.range 0 max_y in
-  List.return (x, y)
+  let* x = List.range 0 max_x in
+  let+ y = List.range 0 max_y in
+  x, y
 ;;
 
 let rays x y grid =
diff --git a/lib/year2022/day09.ml b/lib/year2022/day09.ml
index 81e183d..e28ad29 100644
--- a/lib/year2022/day09.ml
+++ b/lib/year2022/day09.ml
@@ -17,8 +17,8 @@ let dir_p =
 ;;
 
 let step_p =
-  let%map dir = dir_p <* P.char ' '
-  and num = P.integer in
+  let+ dir = dir_p <* P.char ' '
+  and+ num = P.integer in
   dir, num
 ;;
 
diff --git a/lib/year2022/day10.ml b/lib/year2022/day10.ml
index b5d04d7..5b4fd56 100644
--- a/lib/year2022/day10.ml
+++ b/lib/year2022/day10.ml
@@ -6,7 +6,7 @@ type inst =
   | Noop
 
 let addx_p =
-  let%map i = P.string "addx " *> P.signed_integer in
+  let+ i = P.string "addx " *> P.signed_integer in
   [ Noop; AddX i ]
 ;;
 
diff --git a/lib/year2022/day11.ml b/lib/year2022/day11.ml
index d8c62d7..e854da0 100644
--- a/lib/year2022/day11.ml
+++ b/lib/year2022/day11.ml
@@ -25,12 +25,12 @@ let div_test_p = P.string "divisible by " *> P.integer >>| Z.of_int
 let throw_p = P.string "throw to monkey " *> P.integer
 
 let monkey_p =
-  let%map id = P.string "Monkey " *> P.integer <* P.string ":" <* P.end_of_line
-  and items = P.string "  Starting items: " *> items_p <* P.end_of_line
-  and op = P.string "  Operation: " *> op_p <* P.end_of_line
-  and div_test = P.string "  Test: " *> div_test_p <* P.end_of_line
-  and if_true = P.string "    If true: " *> throw_p <* P.end_of_line
-  and if_false = P.string "    If false: " *> throw_p <* P.end_of_line in
+  let+ id = P.string "Monkey " *> P.integer <* P.string ":" <* P.end_of_line
+  and+ items = P.string "  Starting items: " *> items_p <* P.end_of_line
+  and+ op = P.string "  Operation: " *> op_p <* P.end_of_line
+  and+ div_test = P.string "  Test: " *> div_test_p <* P.end_of_line
+  and+ if_true = P.string "    If true: " *> throw_p <* P.end_of_line
+  and+ if_false = P.string "    If false: " *> throw_p <* P.end_of_line in
   { id; items = List.map items ~f:Z.of_int; op; div_test; if_true; if_false }
 ;;
 
diff --git a/lib/year2023/day02.ml b/lib/year2023/day02.ml
index 132b889..529cd6c 100644
--- a/lib/year2023/day02.ml
+++ b/lib/year2023/day02.ml
@@ -24,8 +24,8 @@ let color_p =
 ;;
 
 let draw_p =
-  let%map count = P.integer <* P.char ' '
-  and color = color_p in
+  let+ count = P.integer <* P.char ' '
+  and+ color = color_p in
   { count; color }
 ;;
 
@@ -33,8 +33,8 @@ let draws_p = P.sep_by1 (P.string ", ") draw_p
 let round_p = P.sep_by1 (P.string "; ") draws_p
 
 let game_p =
-  let%map id = P.string "Game " *> P.integer <* P.string ": "
-  and round = round_p in
+  let+ id = P.string "Game " *> P.integer <* P.string ": "
+  and+ round = round_p in
   { id; round }
 ;;
 
diff --git a/lib/year2023/day04.ml b/lib/year2023/day04.ml
index 49d845d..a0357f9 100644
--- a/lib/year2023/day04.ml
+++ b/lib/year2023/day04.ml
@@ -12,9 +12,9 @@ type card =
 let nums_p = P.sep_by1 P.spaces P.integer
 
 let card_p =
-  let%map id = P.string "Card" *> P.spaces *> P.integer <* P.char ':' <* P.spaces
-  and winners = nums_p <* P.spaces <* P.char '|' <* P.spaces
-  and picks = nums_p in
+  let+ id = P.string "Card" *> P.spaces *> P.integer <* P.char ':' <* P.spaces
+  and+ winners = nums_p <* P.spaces <* P.char '|' <* P.spaces
+  and+ picks = nums_p in
   { id; winners = IntSet.of_list winners; picks = IntSet.of_list picks }
 ;;
 
diff --git a/lib/year2023/day05.ml b/lib/year2023/day05.ml
index 0c84b16..10f8376 100644
--- a/lib/year2023/day05.ml
+++ b/lib/year2023/day05.ml
@@ -21,9 +21,9 @@ type almanac =
 let seeds_p = P.string "seeds: " *> P.sep_by1 (P.char ' ') P.integer
 
 let mapping_p =
-  let%map dest = P.integer <* P.char ' '
-  and source = P.integer <* P.char ' '
-  and length = P.integer in
+  let+ dest = P.integer <* P.char ' '
+  and+ source = P.integer <* P.char ' '
+  and+ length = P.integer in
   { source; dest; length }
 ;;
 
@@ -34,16 +34,16 @@ let name_p =
 ;;
 
 let map_p =
-  let%map name = name_p <* P.string " map:" <* P.end_of_line
-  and mappings = P.sep_by1 P.end_of_line mapping_p in
+  let+ name = name_p <* P.string " map:" <* P.end_of_line
+  and+ mappings = P.sep_by1 P.end_of_line mapping_p in
   { name; mappings }
 ;;
 
 let maps_p = P.sep_by1 (P.count 2 P.end_of_line) map_p
 
 let almanac_p =
-  let%map seeds = seeds_p <* P.count 2 P.end_of_line
-  and maps = maps_p in
+  let+ seeds = seeds_p <* P.count 2 P.end_of_line
+  and+ maps = maps_p in
   { seeds; maps }
 ;;
 
diff --git a/lib/year2023/day06.ml b/lib/year2023/day06.ml
index 7ffbc3e..348474b 100644
--- a/lib/year2023/day06.ml
+++ b/lib/year2023/day06.ml
@@ -7,8 +7,8 @@ type race =
   }
 
 let data_p p =
-  let%map times = P.string "Time:" *> P.spaces *> P.sep_by1 P.spaces p <* P.end_of_line
-  and distances = P.string "Distance:" *> P.spaces *> P.sep_by1 P.spaces p in
+  let+ times = P.string "Time:" *> P.spaces *> P.sep_by1 P.spaces p <* P.end_of_line
+  and+ distances = P.string "Distance:" *> P.spaces *> P.sep_by1 P.spaces p in
   times, distances
 ;;
 
@@ -22,7 +22,7 @@ let races_p =
 ;;
 
 let race_p =
-  let%map times, distances = data_p P.digits in
+  let+ times, distances = data_p P.digits in
   { time = times |> String.concat |> Int.of_string
   ; distance = distances |> String.concat |> Int.of_string
   }
diff --git a/lib/year2023/day07.ml b/lib/year2023/day07.ml
index 36d6c45..e830f5a 100644
--- a/lib/year2023/day07.ml
+++ b/lib/year2023/day07.ml
@@ -58,8 +58,8 @@ let card_p =
 ;;
 
 let hand_p =
-  let%map cards = P.many1 card_p <* P.spaces
-  and score = P.integer in
+  let+ cards = P.many1 card_p <* P.spaces
+  and+ score = P.integer in
   cards, score
 ;;
 
diff --git a/lib/year2023/day08.ml b/lib/year2023/day08.ml
index 8f370a1..36f7b1e 100644
--- a/lib/year2023/day08.ml
+++ b/lib/year2023/day08.ml
@@ -24,22 +24,22 @@ let token_p =
 ;;
 
 let pair_p =
-  let%map left = P.char '(' *> token_p <* P.string ", "
-  and right = token_p <* P.char ')' in
+  let+ left = P.char '(' *> token_p <* P.string ", "
+  and+ right = token_p <* P.char ')' in
   left, right
 ;;
 
 let entry_p =
-  let%map key = token_p <* P.string " = "
-  and value = pair_p in
+  let+ key = token_p <* P.string " = "
+  and+ value = pair_p in
   key, value
 ;;
 
 let map_p = P.sep_by1 P.end_of_line entry_p >>| StrMap.of_alist_exn
 
 let input_p =
-  let%map dirs = dirs_p <* P.end_of_line
-  and map = map_p in
+  let+ dirs = dirs_p <* P.end_of_line
+  and+ map = map_p in
   { dirs; map }
 ;;
 
diff --git a/lib/year2023/day12.ml b/lib/year2023/day12.ml
index 6c64bd4..aaad1c1 100644
--- a/lib/year2023/day12.ml
+++ b/lib/year2023/day12.ml
@@ -11,8 +11,8 @@ let is_token = function
 ;;
 
 let line_p =
-  let%map tokens = P.take_while is_token <* P.char ' '
-  and counts = P.sep_by1 (P.char ',') P.integer in
+  let+ tokens = P.take_while is_token <* P.char ' '
+  and+ counts = P.sep_by1 (P.char ',') P.integer in
   String.to_list tokens, counts
 ;;
 
diff --git a/lib/year2023/day13.ml b/lib/year2023/day13.ml
index 5fc3792..debb21a 100644
--- a/lib/year2023/day13.ml
+++ b/lib/year2023/day13.ml
@@ -46,9 +46,9 @@ let reflection_score' g =
     result
   in
   let coords =
-    let open Sequence.Let_syntax in
-    let%bind x = Sequence.range 0 (Array.length g) in
-    let%map y = Sequence.range 0 (Array.length g.(x)) in
+    let open Util.Sequence.Syntax in
+    let* x = Sequence.range 0 (Array.length g) in
+    let+ y = Sequence.range 0 (Array.length g.(x)) in
     x, y
   in
   coords
diff --git a/lib/year2023/day15.ml b/lib/year2023/day15.ml
index c9083c7..db7e78b 100644
--- a/lib/year2023/day15.ml
+++ b/lib/year2023/day15.ml
@@ -29,8 +29,8 @@ let token_p =
 let inst_p = P.choice [ Drop <$ P.char '-'; (P.char '=' *> P.integer >>| fun i -> Add i) ]
 
 let op_p =
-  let%map label = token_p
-  and inst = inst_p in
+  let+ label = token_p
+  and+ inst = inst_p in
   { label; hash = hash label; inst }
 ;;
 
diff --git a/lib/year2023/day17.ml b/lib/year2023/day17.ml
index 7bed490..4aa1114 100644
--- a/lib/year2023/day17.ml
+++ b/lib/year2023/day17.ml
@@ -35,8 +35,7 @@ let solve max drop grid =
   let expand_steps dir init_loss coords =
     coords
     |> List.filter_map ~f:(fun coord ->
-      let%map.Option loss = Map.find grid coord in
-      loss, coord)
+      coord |> Map.find grid |> Option.map ~f:(fun loss -> loss, coord))
     |> List.folding_map ~init:init_loss ~f:(fun sum (loss, coord) ->
       let loss' = sum + loss in
       loss', (loss', coord, dir))
diff --git a/lib/year2023/day18.ml b/lib/year2023/day18.ml
index c92f689..fe00168 100644
--- a/lib/year2023/day18.ml
+++ b/lib/year2023/day18.ml
@@ -24,9 +24,9 @@ let hex_p =
 ;;
 
 let command_p =
-  let%map dir = dir_p <* P.char ' '
-  and length = P.integer <* P.char ' '
-  and color = P.string "(#" *> hex_p <* P.char ')' in
+  let+ dir = dir_p <* P.char ' '
+  and+ length = P.integer <* P.char ' '
+  and+ color = P.string "(#" *> hex_p <* P.char ')' in
   { dir; length; color }
 ;;
 
diff --git a/lib/year2023/day19.ml b/lib/year2023/day19.ml
index 93deacb..035a92b 100644
--- a/lib/year2023/day19.ml
+++ b/lib/year2023/day19.ml
@@ -65,16 +65,16 @@ let state_p = P.choice [ Accept <$ P.char 'A'; Reject <$ P.char 'R' ]
 let dest_p = P.choice [ (state_p >>| fun s -> End s); (name_p >>| fun n -> Name n) ]
 
 let lt_p =
-  let%map attr = attr_p <* P.char '<'
-  and n = P.integer <* P.char ':'
-  and dest = dest_p in
+  let+ attr = attr_p <* P.char '<'
+  and+ n = P.integer <* P.char ':'
+  and+ dest = dest_p in
   LT { attr; n; dest }
 ;;
 
 let gt_p =
-  let%map attr = attr_p <* P.char '>'
-  and n = P.integer <* P.char ':'
-  and dest = dest_p in
+  let+ attr = attr_p <* P.char '>'
+  and+ n = P.integer <* P.char ':'
+  and+ dest = dest_p in
   GT { attr; n; dest }
 ;;
 
@@ -82,29 +82,29 @@ let move_p = dest_p >>| fun d -> Move d
 let rule_p = P.choice [ lt_p; gt_p; move_p ]
 
 let workflow_p =
-  let%map name = name_p <* P.char '{'
-  and rules = P.sep_by1 (P.char ',') rule_p <* P.char '}' in
+  let+ name = name_p <* P.char '{'
+  and+ rules = P.sep_by1 (P.char ',') rule_p <* P.char '}' in
   { name; rules }
 ;;
 
 let workflows_p =
-  let%map workflows = P.sep_by1 P.end_of_line workflow_p in
+  let+ workflows = P.sep_by1 P.end_of_line workflow_p in
   workflows |> List.map ~f:(fun w -> w.name, w) |> StrMap.of_alist_exn
 ;;
 
 let part_p =
-  let%map x = P.string "{x=" *> P.integer <* P.char ','
-  and m = P.string "m=" *> P.integer <* P.char ','
-  and a = P.string "a=" *> P.integer <* P.char ','
-  and s = P.string "s=" *> P.integer <* P.char '}' in
+  let+ x = P.string "{x=" *> P.integer <* P.char ','
+  and+ m = P.string "m=" *> P.integer <* P.char ','
+  and+ a = P.string "a=" *> P.integer <* P.char ','
+  and+ s = P.string "s=" *> P.integer <* P.char '}' in
   { x; m; a; s }
 ;;
 
 let parts_p = P.sep_by1 P.end_of_line part_p
 
 let input_p =
-  let%map workflows = workflows_p <* P.string "\n\n"
-  and parts = parts_p in
+  let+ workflows = workflows_p <* P.string "\n\n"
+  and+ parts = parts_p in
   { workflows; parts }
 ;;
 
diff --git a/lib/year2023/day20.ml b/lib/year2023/day20.ml
index 3b1e49d..e0fe21f 100644
--- a/lib/year2023/day20.ml
+++ b/lib/year2023/day20.ml
@@ -50,26 +50,26 @@ let name_p =
 let outputs_p = P.sep_by1 (P.string ", ") name_p
 
 let broadcaster_p =
-  let%map outputs = P.string "broadcaster -> " *> outputs_p in
+  let+ outputs = P.string "broadcaster -> " *> outputs_p in
   Broadcaster { name = "broadcaster"; outputs }
 ;;
 
 let flip_flop_p =
-  let%map name = P.char '%' *> name_p <* P.string " -> "
-  and outputs = outputs_p in
+  let+ name = P.char '%' *> name_p <* P.string " -> "
+  and+ outputs = outputs_p in
   FlipFlop { name; state = Off; outputs }
 ;;
 
 let conjunction_p =
-  let%map name = P.char '&' *> name_p <* P.string " -> "
-  and outputs = outputs_p in
+  let+ name = P.char '&' *> name_p <* P.string " -> "
+  and+ outputs = outputs_p in
   Conjunction { name; last_inputs = StrMap.empty; outputs }
 ;;
 
 let module_p = P.choice [ flip_flop_p; conjunction_p; broadcaster_p ]
 
 let modules_p =
-  let%map modules = P.sep_by1 P.end_of_line module_p in
+  let+ modules = P.sep_by1 P.end_of_line module_p in
   modules |> List.map ~f:(fun m -> mod_name m, m) |> StrMap.of_alist_exn
 ;;
 
diff --git a/lib/year2023/day22.ml b/lib/year2023/day22.ml
index 06393a0..6987f72 100644
--- a/lib/year2023/day22.ml
+++ b/lib/year2023/day22.ml
@@ -15,20 +15,20 @@ end
 module BrickSet = Set.Make (Brick)
 
 let coord_p =
-  let%map x = P.integer <* P.char ','
-  and y = P.integer <* P.char ','
-  and z = P.integer in
+  let+ x = P.integer <* P.char ','
+  and+ y = P.integer <* P.char ','
+  and+ z = P.integer in
   { x; y; z }
 ;;
 
 let brick_p =
-  let%map a = coord_p <* P.char '~'
-  and b = coord_p in
+  let+ a = coord_p <* P.char '~'
+  and+ b = coord_p in
   a, b
 ;;
 
 let bricks_p =
-  let%map bricks = P.sep_by1 P.end_of_line brick_p in
+  let+ bricks = P.sep_by1 P.end_of_line brick_p in
   bricks |> List.mapi ~f:(fun i (a, b) -> i, a, b) |> BrickSet.of_list
 ;;
 
diff --git a/lib/year2023/day24.ml b/lib/year2023/day24.ml
index 6f80fcd..1a12395 100644
--- a/lib/year2023/day24.ml
+++ b/lib/year2023/day24.ml
@@ -17,12 +17,12 @@ type line =
   }
 
 let stone_p =
-  let%map x = P.signed_integer <* P.char ',' <* P.spaces >>| Q.of_int
-  and y = P.signed_integer <* P.char ',' <* P.spaces >>| Q.of_int
-  and z = P.signed_integer <* P.spaces <* P.char '@' <* P.spaces >>| Q.of_int
-  and dx = P.signed_integer <* P.char ',' <* P.spaces >>| Q.of_int
-  and dy = P.signed_integer <* P.char ',' <* P.spaces >>| Q.of_int
-  and dz = P.signed_integer >>| Q.of_int in
+  let+ x = P.signed_integer <* P.char ',' <* P.spaces >>| Q.of_int
+  and+ y = P.signed_integer <* P.char ',' <* P.spaces >>| Q.of_int
+  and+ z = P.signed_integer <* P.spaces <* P.char '@' <* P.spaces >>| Q.of_int
+  and+ dx = P.signed_integer <* P.char ',' <* P.spaces >>| Q.of_int
+  and+ dy = P.signed_integer <* P.char ',' <* P.spaces >>| Q.of_int
+  and+ dz = P.signed_integer >>| Q.of_int in
   { x; y; z; dx; dy; dz }
 ;;
 
diff --git a/lib/year2023/day25.ml b/lib/year2023/day25.ml
index e78c33e..bfeca0c 100644
--- a/lib/year2023/day25.ml
+++ b/lib/year2023/day25.ml
@@ -19,8 +19,8 @@ let token_p =
 ;;
 
 let line_p =
-  let%map node = token_p <* P.string ": "
-  and nodes = P.sep_by1 (P.char ' ') token_p in
+  let+ node = token_p <* P.string ": "
+  and+ nodes = P.sep_by1 (P.char ' ') token_p in
   node, nodes
 ;;