diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2ee1d35
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,8 @@
+_build/
+setup.data
+setup.log
+*.byte
+*.native
+*/*.mldylib
+*/*.mllib
+*.docdir
diff --git a/.merlin b/.merlin
new file mode 100644
index 0000000..664e581
--- /dev/null
+++ b/.merlin
@@ -0,0 +1,4 @@
+S src
+B _build/**
+
+PKG cmdliner
diff --git a/.ocamlinit b/.ocamlinit
new file mode 100644
index 0000000..341d086
--- /dev/null
+++ b/.ocamlinit
@@ -0,0 +1,16 @@
+(* -*- mode: tuareg -*- *)
+
+(* Added by OPAM. *)
+let () =
+  try Topdirs.dir_directory (Sys.getenv "OCAML_TOPLEVEL_PATH")
+  with Not_found -> ()
+;;
+
+#directory "_build/src"
+#use "topfind"
+#require "bytes"
+#load "wshiml.cma"
+
+#require "ppx_deriving.std"
+let pp_int_couple = Ymse.Couple.pp Format.pp_print_int;;
+#install_printer pp_int_couple;;
diff --git a/CHANGES.md b/CHANGES.md
new file mode 100644
index 0000000..e69de29
diff --git a/COPYING b/COPYING
new file mode 100644
index 0000000..c4792dd
--- /dev/null
+++ b/COPYING
@@ -0,0 +1,515 @@
+
+                  GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 2.1, February 1999
+
+ Copyright (C) 1991, 1999 Free Software Foundation, Inc.
+     59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+[This is the first released version of the Lesser GPL.  It also counts
+ as the successor of the GNU Library Public License, version 2, hence
+ the version number 2.1.]
+
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diff --git a/DEVEL.md b/DEVEL.md
new file mode 100644
index 0000000..e69de29
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..3639f14
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,41 @@
+# OASIS_START
+# DO NOT EDIT (digest: a3c674b4239234cbbe53afe090018954)
+
+SETUP = ocaml setup.ml
+
+build: setup.data
+	$(SETUP) -build $(BUILDFLAGS)
+
+doc: setup.data build
+	$(SETUP) -doc $(DOCFLAGS)
+
+test: setup.data build
+	$(SETUP) -test $(TESTFLAGS)
+
+all:
+	$(SETUP) -all $(ALLFLAGS)
+
+install: setup.data
+	$(SETUP) -install $(INSTALLFLAGS)
+
+uninstall: setup.data
+	$(SETUP) -uninstall $(UNINSTALLFLAGS)
+
+reinstall: setup.data
+	$(SETUP) -reinstall $(REINSTALLFLAGS)
+
+clean:
+	$(SETUP) -clean $(CLEANFLAGS)
+
+distclean:
+	$(SETUP) -distclean $(DISTCLEANFLAGS)
+
+setup.data:
+	$(SETUP) -configure $(CONFIGUREFLAGS)
+
+configure:
+	$(SETUP) -configure $(CONFIGUREFLAGS)
+
+.PHONY: build doc test all install uninstall reinstall clean distclean configure
+
+# OASIS_STOP
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..881dcda
--- /dev/null
+++ b/README.md
@@ -0,0 +1,28 @@
+Wshiml
+========
+
+Implementation of
+http://nlp.stanford.edu/IR-book/html/htmledition/near-duplicates-and-shingling-1.html
+
+Build requires [oasis](http://oasis.forge.ocamlcore.org/index.html). Do:
+
+    ./configure    # optionally with --prefix
+    make
+    make install
+
+To build the example command-line program, do
+
+    ./configure --enable-cli
+    make
+    make install
+    find-similar-docs --help
+
+The command-line program requires
+[cmdliner](http://erratique.ch/software/cmdliner). The rest of the
+software has no dependencies apart from Oasis for building from git.
+
+So far the code is completely unoptimised apart from what's described
+in
+http://nlp.stanford.edu/IR-book/html/htmledition/near-duplicates-and-shingling-1.html
+and uses 12s (9s with super-shingling) to cluster 1458 documents of
+altogether 556176 words on an old 2.8 GHz AMD.
diff --git a/_oasis b/_oasis
new file mode 100644
index 0000000..d5970cd
--- /dev/null
+++ b/_oasis
@@ -0,0 +1,40 @@
+OASISFormat: 0.4
+Name:        wshiml
+Version:     0.1.0
+Synopsis:    Near-duplicate document detection by word shingling
+Authors:     Kevin Brubeck Unhammer
+License:     LGPL-2.1 with OCaml linking exception
+BuildTools:  ocamlbuild
+Plugins:     META (0.4), DevFiles (0.4)
+
+Description: Near-duplicate document detection by word shingling; library and example command line program.
+Homepage:    https://github.com/unhammer/wshiml
+
+Library "wshiml"
+  Path:       src
+  Modules:    Wshiml
+  InternalModules: Ymse
+
+Flag "cli"
+  Description: Install example command line program to find similar docs
+  Default: false
+
+Executable "find-similar-docs"
+  Build$: flag(cli)
+  Install$: flag(cli)
+  Path:       examples
+  MainIs:     find_similar_docs.ml
+  BuildDepends: wshiml, cmdliner
+  CompiledObject: best
+
+
+AlphaFeatures: ocamlbuild_more_args
+
+Document "wshiml_api"
+  Type: ocamlbuild (0.4)
+  BuildTools: ocamldoc
+  Title: API reference for Wshiml
+  XOCamlbuildPath: .
+  XOCamlbuildExtraArgs:
+    "-docflags '-colorize-code -short-functors -charset utf-8'"
+  XOCamlbuildLibraries: wshiml
diff --git a/configure b/configure
new file mode 100755
index 0000000..6acfaeb
--- /dev/null
+++ b/configure
@@ -0,0 +1,27 @@
+#!/bin/sh
+
+# OASIS_START
+# DO NOT EDIT (digest: dc86c2ad450f91ca10c931b6045d0499)
+set -e
+
+FST=true
+for i in "$@"; do
+  if $FST; then
+    set --
+    FST=false
+  fi
+
+  case $i in
+    --*=*)
+      ARG=${i%%=*}
+      VAL=${i##*=}
+      set -- "$@" "$ARG" "$VAL"
+      ;;
+    *)
+      set -- "$@" "$i"
+      ;;
+  esac
+done
+
+ocaml setup.ml -configure "$@"
+# OASIS_STOP
diff --git a/examples/find_similar_docs.ml b/examples/find_similar_docs.ml
new file mode 100644
index 0000000..61391be
--- /dev/null
+++ b/examples/find_similar_docs.ml
@@ -0,0 +1,67 @@
+let slurp_file filename =
+  let lines = ref [] in
+  let chan = open_in filename in
+  let rl = try
+      while true; do
+        lines := input_line chan :: !lines
+      done; !lines
+    with End_of_file ->
+      close_in chan;
+      !lines
+  in
+  List.rev rl |> Bytes.concat "\n"
+
+let print_clusters (files: bytes array) (clusters: Wshiml.clusters) =
+  List.filter (function a::b::_ -> true | _ -> false) clusters
+  |> List.map (fun l -> List.map (Array.get files) l |> Bytes.concat "\t")
+  |> Bytes.concat "\n"
+  |> print_endline
+
+let print_scores =
+  List.iter (fun ((d1,d2),score) -> Printf.printf "%d & %d = %d\n" d1 d2 score)
+
+
+let find_similar_docs threshold super files =
+  let files_a = Array.of_list files in
+  let ndocs = Array.length files_a in
+  Wshiml.sketch_docs ~slurp_file files
+  |> (fun sketch -> if super then Wshiml.supersketches sketch else sketch)
+  |> Wshiml.score_sketches ~threshold
+  (* DEBUG: *)
+  (* |> (fun scores -> print_scores scores; print_endline ""; scores) *)
+  |> Wshiml.cluster_scores ~ndocs
+  |> print_clusters files_a
+
+
+open Cmdliner
+
+let super =
+  let doc = "Create a super-shingle (shingle of shingles) before clustering. May speed up clustering." in
+  Arg.(value & flag & info ["s"; "super"] ~docv:"SUPER" ~doc)
+
+let threshold =
+  let doc = "The overlap threshold for considering two documents similar." in
+  Arg.(value & opt float 0.8 & info ["t"; "threshold"] ~docv:"THRESHOLD" ~doc)
+
+let files =
+  let doc = "The documents to compare." in
+  Arg.(non_empty & pos_all file [] & info [] ~docv:"FILES" ~doc)
+
+let fnd_t = Term.(pure find_similar_docs $ threshold $ super $ files)
+
+let info =
+  let doc = "find similar or near duplicate documents" in
+  let man = [
+    `S "DESCRIPTION";
+    `P "$(tname) uses word shingling to find near duplicate or similar
+        documents among files specified on the command line.";
+    `P "The output is tab-separated, one cluster per line.";
+    `P "Note that the comparison is probabilistic, and results may
+        differ between runs.";
+    `S "BUGS";
+    `P "Email bug reports to <unhammer at fsfe.org>.";
+  ] in
+  Term.info "find-similar-docs" ~version:"0.1.0" ~doc ~man
+
+let () =
+  match Term.eval (fnd_t, info) with `Error _ -> exit 1 | _ -> exit 0
diff --git a/setup.ml b/setup.ml
new file mode 100644
index 0000000..0345fe1
--- /dev/null
+++ b/setup.ml
@@ -0,0 +1,37 @@
+(* setup.ml generated for the first time by OASIS v0.4.5 *)
+
+(* OASIS_START *)
+(* DO NOT EDIT (digest: 9852805d5c19ca1cb6abefde2dcea323) *)
+(******************************************************************************)
+(* OASIS: architecture for building OCaml libraries and applications          *)
+(*                                                                            *)
+(* Copyright (C) 2011-2013, Sylvain Le Gall                                   *)
+(* Copyright (C) 2008-2011, OCamlCore SARL                                    *)
+(*                                                                            *)
+(* This library is free software; you can redistribute it and/or modify it    *)
+(* under the terms of the GNU Lesser General Public License as published by   *)
+(* the Free Software Foundation; either version 2.1 of the License, or (at    *)
+(* your option) any later version, with the OCaml static compilation          *)
+(* exception.                                                                 *)
+(*                                                                            *)
+(* This library is distributed in the hope that it will be useful, but        *)
+(* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY *)
+(* or FITNESS FOR A PARTICULAR PURPOSE. See the file COPYING for more         *)
+(* details.                                                                   *)
+(*                                                                            *)
+(* You should have received a copy of the GNU Lesser General Public License   *)
+(* along with this library; if not, write to the Free Software Foundation,    *)
+(* Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA              *)
+(******************************************************************************)
+
+let () =
+  try
+    Topdirs.dir_directory (Sys.getenv "OCAML_TOPLEVEL_PATH")
+  with Not_found -> ()
+;;
+#use "topfind";;
+#require "oasis.dynrun";;
+open OASISDynRun;;
+
+(* OASIS_STOP *)
+let () = setup ();;
diff --git a/src/wshiml.ml b/src/wshiml.ml
new file mode 100644
index 0000000..e1b6c26
--- /dev/null
+++ b/src/wshiml.ml
@@ -0,0 +1,186 @@
+open Ymse
+
+module Bset = Set.Make(Bytes)
+module Hset = Set.Make(struct type t = int let compare = compare end)
+
+module PiMap = struct
+  include Map.Make(struct type t = int * int let compare = compare end)
+  let append k v map =
+    try
+      let old = find k map in add k (v::old) map
+    with
+      Not_found -> add k [v] map
+end
+
+module DupeMap = struct
+  include Map.Make(struct type t = int Couple.t let compare = compare end)
+  let bump map k =
+    try
+      let old = find k map in add k (old+1) map
+    with
+      Not_found -> add k 1 map
+end
+
+
+let simple_tokenise_on =
+  Bytes.to_set " \n\t.-;:?+,()[]{}<>\\/$%&#@*~_«»"
+
+let simple_tokenise doc =
+  Bytes.split (fun c -> Cset.mem c simple_tokenise_on) doc
+
+
+let jacquard s1 s2 =
+  let f_len set = Bset.cardinal set |> float_of_int in
+  let l_inter = f_len (Bset.inter s1 s2) in
+  let l_union = f_len (Bset.union s1 s2) in
+  l_inter /. l_union
+
+let jacquard_hash s1 s2 =
+  let f_len set = Hset.cardinal set |> float_of_int in
+  let l_inter = f_len (Hset.inter s1 s2) in
+  let l_union = f_len (Hset.union s1 s2) in
+  l_inter /. l_union
+
+let shingles n l =
+  let rec aux todo acc =
+    if List.length todo <= n then
+      todo::acc
+    else let shingle = List.take n todo in
+      aux (List.tl todo) (shingle::acc)
+  in
+  aux l []
+
+let shingleset_of_doc ?(tokenise=simple_tokenise) ?(n=4) doc =
+  tokenise doc
+  |> shingles n
+  |> List.map (Bytes.concat " ")
+  |> Bset.of_list
+
+let compare_docs ?(tokenise=simple_tokenise) ?(n=4) d1 d2 =
+  if d1 = d2 then 1.0
+  else
+    let prep d = shingleset_of_doc ~tokenise ~n d in
+    jacquard (prep d1) (prep d2)
+
+(* If we want to extract potential duplicates from many documents,
+   comparing the cross product of all documents gets real slow.
+   Instead, we do a probabilistic comparison of the hashes of the
+   shingles. *)
+let hashes_of_doc ?(tokenise=simple_tokenise) ?(n=4) doc =
+  tokenise doc
+  |> shingles n
+  |> List.map Hashtbl.hash
+
+(* If π is a random permutation from hashest to hashes, then Π(d) is
+   the set of permuted hashes in H(d); so for each h ∈ H(d) there is
+   a corresponding π(h) ∈ Π(d).
+
+   Since we can have several random permutations, an actual π is
+   parametrised by random number `r` *)
+let n_permutations = 200
+let randoms =
+  Random.self_init ();
+  let rec aux acc = function
+    | 0 -> acc
+    | n -> aux (Hashtbl.hash (Random.int64 (Int64.max_int))::acc) (n-1)
+    (* Call .hash on the random to make sure it's in the same range as
+       other .hash values *)
+  in
+  aux [] n_permutations
+(* TODO: randoms should probably be parametrised somehow (at the very
+   least it should be possible to give a seed, for testing), but it's
+   important that the same list is reused for each document in order
+   for the comparisons to make sense. Need a safe way to ensure caller
+   doesn't mess that up. *)
+
+let pi r hash = r lxor hash
+
+(* Randomiser and the minimal element of the random-permuted hash *)
+type minpi = int * int
+let min_pi hashes r =
+  let min_elt = List.map (pi r) hashes
+                |> List.min_elt max_int
+  in
+  (r, min_elt)
+
+(* The probability of two documents having the same minimal element
+   in Π for some r, is the same as the probability of them having
+   the same Jacquard coefficient. Thus we compute Π repeatedly (for
+   200 values of `r`), and pick the minimal element xr₁ from each
+   set; this is the sketch φ(d) of d. Our estimate of the Jacquard
+   coefficient is now |φ₁ ∩ φ₂|/200. *)
+type sketch = minpi list
+type tokeniser = bytes -> bytes list
+let sketch_of_doc ?(tokenise=simple_tokenise) ?(n=4) doc =
+  let hashes = hashes_of_doc ~tokenise ~n doc in
+  List.map (min_pi hashes) randoms
+
+type sketchdocs = (sketch * int) list
+
+let id x = x
+
+let sketch_docs ?(tokenise=simple_tokenise) ?(n=4) ?(slurp_file=id) docs =
+  List.mapi
+    (fun i_d path -> (sketch_of_doc ~tokenise ~n (slurp_file path), i_d))
+    docs
+
+(* TODO: For speedup: only compare those documents that have a
+   _supershingle_ in common. *)
+let supershingles ?(n=4) sketch =
+  List.sort compare sketch |> shingles n
+
+let hashes_of_sketch ?(n=4) sketch =
+  supershingles ~n sketch
+  |> List.map Hashtbl.hash
+
+let supersketch ?(n=4) sketch =
+  let hashes = hashes_of_sketch ~n sketch in
+  List.map (min_pi hashes) randoms
+
+let supersketches ?(n=4) sketches =
+  List.map (fun (sketch,i_d) -> supersketch sketch, i_d) sketches
+
+(* Now we create a map from minimal elements xr₁ to the documents
+   (indices) that contain this element: *)
+let pimap_of_sketches sketches =
+  List.fold_left
+    (fun map (s, i_d) ->
+       List.fold_left (fun m' minpi -> PiMap.append minpi i_d m')
+         map
+         s)
+    PiMap.empty
+    sketches
+
+(* … and then we reverse that to a map from document-pairs to the
+   number of shingles they have in common:*)
+let dupescore_of_pimap pimap =
+  PiMap.fold (fun minpi docs map ->
+      List.allpairs docs
+      |> List.map Couple.create
+      |> List.fold_left DupeMap.bump map
+    ) pimap DupeMap.empty
+  |> DupeMap.bindings
+  |> List.sort (fun (_,c1) (_,c2) -> compare c2 c1)
+
+(* This should let us start clustering those documents that have more
+   than a certain threshold of elements in common. *)
+type scoreddocs = ((int * int) * int) list
+
+let score_sketches ?(threshold=0.8) sketches =
+  let threshold = float_of_int n_permutations *. threshold |> int_of_float in
+  pimap_of_sketches sketches
+  |> dupescore_of_pimap
+  |> List.filter (fun (_,s) -> s > threshold)
+  |> List.map (fun (k,s) -> (Couple.get k, s))
+
+type clusters = int list list
+
+let top_doc_ind scores =
+  List.map fst scores |> List.fold_left (fun top (a,b) -> max top (max a b)) 0
+
+let cluster_scores ?(ndocs=0) scores =
+  let ndocs = if ndocs > 0 then ndocs else top_doc_ind scores in
+  let ds = DisjointSet.init ndocs in
+  List.map fst scores (* ignore scores! anything surviving threshold is A-ok *)
+  |> List.iter (DisjointSet.union ds);
+  DisjointSet.to_lists ds
diff --git a/src/wshiml.mli b/src/wshiml.mli
new file mode 100644
index 0000000..75e087c
--- /dev/null
+++ b/src/wshiml.mli
@@ -0,0 +1,43 @@
+(** Word shingling for near duplicate document detection. *)
+
+(** A sketch of one document. A sketch is the set of minimal elements
+    that result from xor-ing the hash of shingles with a list of
+    random hashes. *)
+type sketch
+
+(** List of sketched documents – the second part of the tuple is a
+    document ID. *)
+type sketchdocs = (sketch * int) list
+
+(** The functions taking documents let you specify your own tokeniser.
+    If a tokeniser is not provided, a very simple
+    whitespace/punctuation tokeniser is used. *)
+type tokeniser = bytes -> bytes list
+
+(** The [n] in the below functions is the number of shingles to use;
+    defaults to 4. *)
+
+(** Compares two documents "exactly", by taking the Jacquard
+    coefficient of the shingles themselves. *)
+val compare_docs : ?tokenise:tokeniser -> ?n:int -> bytes -> bytes -> float
+
+val sketch_of_doc : ?tokenise:tokeniser -> ?n:int -> bytes -> sketch
+
+(** @param slurp_file If provided, called on each document before processing (lets you pass a list of filenames instead of a list of the full documents). *)
+val sketch_docs : ?tokenise:tokeniser -> ?n:int -> ?slurp_file:(bytes -> bytes) -> bytes list -> sketchdocs
+
+
+val supersketches : ?n:int -> sketchdocs -> sketchdocs
+
+
+(** Document-pair (as indices) to score. *)
+type scoreddocs = ((int * int) * int) list
+
+val score_sketches : ?threshold:float -> sketchdocs -> scoreddocs
+
+(** List of clusters; documents referred to by their index in the
+    original list. *)
+type clusters = int list list
+
+(** @param ndocs Number of documents. If not provided, uses the highest index in [scoreddocs]. *)
+val cluster_scores : ?ndocs:int -> scoreddocs -> clusters
diff --git a/src/ymse.ml b/src/ymse.ml
new file mode 100644
index 0000000..b9977b2
--- /dev/null
+++ b/src/ymse.ml
@@ -0,0 +1,133 @@
+
+module List = struct
+  include List
+  let take n l =
+    let rec aux n acc = function
+    | [] -> acc
+    | hd::tl ->
+        if n > 0 then
+          aux (n-1) (hd::acc) tl
+        else acc
+    in
+    aux n [] l
+    |> rev
+
+  let rec min_elt min = function
+    | [] -> min
+    | (hd::tl) when hd < min -> min_elt hd tl
+    | (_::tl) -> min_elt min tl
+
+  let allpairs l =
+    let rec aux seen acc = function
+    | a::tl -> let with_a = List.map (fun e -> (e,a)) seen in
+        aux (a::seen) (with_a::acc) tl
+    | [] -> acc
+    in
+    aux [] [] l
+    |> List.concat
+end
+
+module Cset = Set.Make(Char)
+
+module Bytes = struct
+  include Bytes
+
+  let split p s =
+    let slice i j = sub s i (j-i) in
+    let rec aux i j acc =
+      if j < length s then
+        begin
+          let elt = get s j in
+          let j1 = j + 1 in
+          if p elt then
+            aux j1 j1 (slice i j::acc)
+          else
+          aux i j1 acc
+        end
+      else (slice i j::acc)
+    in
+    aux 0 0 []
+    |> List.filter (fun s -> length s > 0)
+    |> List.rev
+
+  let to_set bytes =
+    let rec aux i acc =
+      if i < length bytes then
+        aux (i+1) (Cset.add (get bytes i) acc)
+      else acc
+    in
+    aux 0 Cset.empty
+end
+
+module Couple : sig
+  (* A "sorted pair" / two-element set, so (a,b)=(b,a) *)
+  type 'a t [@@deriving show]
+  val create : 'a * 'a -> 'a t
+  val get: 'a t -> 'a * 'a
+end = struct
+  type 'a t = 'a * 'a [@@deriving show]
+  let create (a, b) = if a < b then (a,b) else (b,a)
+  let get a = a
+end
+
+
+module DisjointSet : sig
+  (* From https://www.cs.cornell.edu/courses/CS3110/2012fa/recitations/rec14.html *)
+
+  (* type node *)
+  type node = { mutable parent : int; mutable rank : int }
+  type t = node array
+
+  val union : t -> int * int -> unit
+  val init : int -> t
+  val find : t -> int -> int
+
+  val to_lists : t -> int list list
+
+end = struct
+
+  type node = { mutable parent : int; mutable rank : int }
+  type t = node array
+
+  let empty_node parent = { parent; rank = 0 }
+
+  let init size = Array.init size empty_node
+
+  let rec find s e =
+    let n = s.(e) in
+    if n.parent = e then e
+    else
+      (n.parent <- (find s n.parent);
+       n.parent)
+
+  let union s (e1, e2) =
+    let r1 = find s e1 and r2 = find s e2 in
+    let n1 = s.(r1) and n2 = s.(r2) in
+    if r1 != r2 then
+      if n1.rank < n2.rank then
+        n1.parent <- r2
+      else if n1.rank > n2.rank then
+        n2.parent <- r1
+      else
+        (n2.parent <- r1; n1.rank <- n1.rank + 1)
+
+  (* A little helper to turn DisjointSet's into lists of lists *)
+  module DSMap = struct
+    include Map.Make(struct type t = int let compare = compare end)
+    let append k v map =
+      try
+        let old = find k map in add k (v::old) map
+      with
+        Not_found -> add k [v] map
+  end
+
+  let to_lists s =
+    let rec aux i map =
+      if i >= Array.length s then map
+      else
+        let map = DSMap.append (find s i) i map in
+        aux (i+1) map
+    in
+    aux 0 DSMap.empty |> DSMap.bindings |> List.map snd
+
+end