build.sh

$ atdgen -t src/hn_item.atd && atdgen -j src/hn_item.atd && make clean && make && echo "Starting up..." && ./odaba.native 
ocaml setup.ml -clean 
ocaml setup.ml -build 
ocamlfind ocamlopt unix.cmxa -I /usr/local/lib/ocaml/ocamlbuild /usr/local/lib/ocaml/ocamlbuild/ocamlbuildlib.cmxa -linkpkg myocamlbuild.ml /usr/local/lib/ocaml/ocamlbuild/ocamlbuild.cmx -o myocamlbuild
/Users/s/.opam/system/bin/ocamlfind ocamldep -package yojson -package threads -package opium -package irmin.unix -package irmin -package core -package cohttp -package biniou -package atdgen -package atd -modules src/odaba.ml > src/odaba.ml.depends
/Users/s/.opam/system/bin/ocamlfind ocamlc -c -w +9+27+32 -warn-error +a -g -annot -bin-annot -thread -package yojson -package threads -package opium -package irmin.unix -package irmin -package core -package cohttp -package biniou -package atdgen -package atd -I src -o src/odaba.cmo src/odaba.ml
+ /Users/s/.opam/system/bin/ocamlfind ocamlc -c -w +9+27+32 -warn-error +a -g -annot -bin-annot -thread -package yojson -package threads -package opium -package irmin.unix -package irmin -package core -package cohttp -package biniou -package atdgen -package atd -I src -o src/odaba.cmo src/odaba.ml
File "src/odaba.ml", line 26, characters 35-42:
Error: This expression has type tx_datom list
       but an expression was expected of type datom
Command exited with code 2.
E: Failure("Command ''/usr/local/bin/ocamlbuild' src/odaba.native -use-ocamlfind -cflags '-w +9+27+32 -warn-error +a' -tag debug' terminated with error code 10")
make: *** [build] Error 1

odaba.ml

type db_value = 
  | S of string
  | I of int

type tx_datom =
    {
      e : int;
      a : string;
      v : db_value;
    }

type datom =
    { 
      e : int;
      a : string;
      v : db_value;
      t : int;
    }

(* Goal is to take a list of tx_datom (which don't have a t
timestamp), convert them to a datom, and add them to the db *)
let transact : datom list -> tx_datom list -> datom list =
  fun db txn ->
  let new_datoms = List.map (fun (txn_dtm : tx_datom list) ->
                             {
                               e = txn_dtm.e;
                               a = txn_dtm.a;
                               v = txn_dtm.v;
                               t = 0;
                             }) txn
  in
  List.append db new_datoms

let (db : datom list) = []

let db' =
  transact db 
  [{e = 1;
    a = "age";
    v = I 31}
  ; {e = 1;
     a = "first_name";
     v = S "Sean"}
  ; {e = 1;
     a = "last_name";
     v = S "Grove"}
  ; {e = 1;
     a = "color";
     v = S "Blue";}]

let db'' =
  transact db'
           [{e = 1;
             a = "language";
             v = S "OCaml";}
           ; {e = 2;
              a = "first_name";
              v = S "Daniel";}
           ; {e = 2;
              a = "last_name";
              v = S "Woelfel";}
           ; {e = 2;
              a = "color";
              v = S "Red";}
           ; {e = 2;
              a = "language";
              v = S "Clojure";}]

let entity db eid =
  let table = Core.Std.String.Table.create () ~size:4 in
  List.iter (fun dtm ->
             if dtm.e = eid then
               Core.Std.Hashtbl.set table ~key:dtm.a ~data:dtm) db;
  table

exception Key_not_found of string

let sf key ent =
  match Core.Std.Hashtbl.find ent key with
  | Some {v = S x; _} -> x
  | Some {v = I x; _} -> string_of_int x
  | None -> raise (Key_not_found "Runtime crash!")

let language ent = sf "language" ent
let name ent = sf "first_name" ent

let () =
  let daniel = entity db'' 2 in
  let sean = entity db'' 1 in
  print_endline ((name sean) ^ " dabbles in " ^ (language sean));
  print_endline ((name daniel) ^ " dabbles in " ^ (language daniel))