first

.gitignore

@@ -0,0 +1,2 @@
+_build
+.merlin

aoc2020.ml

@@ -0,0 +1,6 @@
+let days = [|Day1.main|]
+
+let _ =
+  match Array.to_list Sys.argv with
+  | _exename :: day :: args -> days.(int_of_string day - 1) args
+  | _ -> Usage.exit "[day_num] args..."

day1.ml

@@ -0,0 +1,6 @@
+let main2 _input =
+  print_endline "boop"
+
+let main = function
+  | [input] -> main2 input
+  | _ -> failwith "usage: $0 1 infile"

dune

@@ -0,0 +1,2 @@
+(executable
+  (name aoc2020))

dune-project

@@ -0,0 +1 @@
+(lang dune 2.7)

usage.ml

@@ -0,0 +1,4 @@
+let exit args =
+  let err = Format.sprintf "usage: %s %s" Sys.argv.(0) args in
+  print_endline err;
+  exit 1