diff -r 2bc119fc8657 -r 94824659f6d7 progs/ocaml/re.ml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/ocaml/re.ml	Fri Aug 15 14:10:58 2014 +0100
@@ -0,0 +1,394 @@
+
+type rexp =
+   NULL 
+ | EMPTY 
+ | CHAR of char
+ | ALT of rexp * rexp
+ | SEQ of rexp * rexp 
+ | STAR of rexp 
+ | RECD of string * rexp;;
+
+type value =
+   Void
+ | Chr of char
+ | Sequ of value * value
+ | Left of value
+ | Right of value
+ | Stars of value list
+ | Rec of string * value;;
+
+let rec string_of_val v = match v with
+   Void -> "Void"
+ | Chr(c) -> String.make 1 c
+ | Sequ(v1, v2) -> "Seq(" ^ string_of_val v1 ^ "," ^ string_of_val v2 ^ ")"
+ | Left(v1) -> "Left(" ^ string_of_val v1 ^ ")"
+ | Right(v1) -> "Right(" ^ string_of_val v1 ^ ")"
+ | Stars(vs) -> "[" ^ String.concat "," (List.map string_of_val vs) ^ "]"
+ | Rec(x, v1) -> x ^ " $ " ^ string_of_val v1;;
+
+
+(* some helper functions for strings *)   
+let explode s =
+  let rec exp i l =
+    if i < 0 then l else exp (i - 1) (s.[i] :: l) in
+  exp (String.length s - 1) [];;
+
+let string_repeat s n =
+  Array.fold_left (^) "" (Array.make n s);;
+
+(* some helper functions for rexps *)
+let rec seq s = match s with
+    [] -> EMPTY
+  | [c] -> CHAR(c)
+  | c::cs -> SEQ(CHAR(c), seq cs);;
+
+let chr c = CHAR(c)
+
+let str s = seq(explode s);;
+
+let plus r = SEQ(r, STAR(r));;
+
+let (++) r1 r2 = ALT(r1, r2);;
+
+let (--) r1 r2 = SEQ(r1, r2);;
+
+let ($) x r = RECD(x, r);;
+
+let alts rs = match rs with 
+    [] -> NULL
+  | [r] -> r
+  | r::rs -> List.fold_left (++) r rs;;
+
+
+(* size of a regular expressions - for testing purposes *)
+let rec size r = match r with
+    NULL -> 1
+  | EMPTY -> 1
+  | CHAR(_) -> 1
+  | ALT(r1, r2) -> 1 + (size r1) + (size r2)
+  | SEQ(r1, r2) -> 1 + (size r1) + (size r2)
+  | STAR(r) -> 1 + (size r)
+  | RECD(_, r) -> 1 + (size r);;
+
+(* nullable function: tests whether the regular 
+   expression can recognise the empty string *)
+let rec nullable r = match r with
+    NULL -> false
+  | EMPTY -> true
+  | CHAR(_) -> false
+  | ALT(r1, r2) -> nullable(r1) || nullable(r2)
+  | SEQ(r1, r2) -> nullable(r1) && nullable(r2)
+  | STAR(_) -> true
+  | RECD(_, r) -> nullable(r);;
+
+(* derivative of a regular expression r w.r.t. a character c *)
+let rec der c r = match r with 
+    NULL -> NULL
+  | EMPTY -> NULL
+  | CHAR(d) -> if c = d then EMPTY else NULL
+  | ALT(r1, r2) -> ALT(der c r1, der c r2)
+  | SEQ(r1, r2) -> 
+      if nullable r1 then ALT(SEQ(der c r1, r2), der c r2)
+      else SEQ(der c r1, r2)
+  | STAR(r) -> SEQ(der c r, STAR(r))
+  | RECD(_, r) -> der c r;;
+
+(* derivative w.r.t. a list of chars (iterates der) *)
+let rec ders s r = match s with 
+    [] -> r
+  | c::s -> ders s (der c r);;
+
+(* extracts a string from value *)
+let rec flatten v = match v with 
+    Void -> ""
+  | Chr(c) -> String.make 1 c
+  | Left(v) -> flatten v
+  | Right(v) -> flatten v
+  | Sequ(v1, v2) -> flatten v1 ^ flatten v2
+  | Stars(vs) -> String.concat "" (List.map flatten vs)
+  | Rec(_, v) -> flatten v;;
+
+
+(* extracts an environment from a value *)
+let rec env v = match v with
+    Void -> []
+  | Chr(c) -> []
+  | Left(v) -> env v
+  | Right(v) -> env v
+  | Sequ(v1, v2) -> env v1 @ env v2
+  | Stars(vs) -> List.flatten (List.map env vs)
+  | Rec(x, v) -> (x, flatten v) :: env v;;
+
+let string_of_pair (x, s) = "(" ^ x ^ "," ^ s ^ ")";;
+let string_of_env xs = String.concat "," (List.map string_of_pair xs);;
+
+
+(* the value for a nullable rexp *)
+let rec mkeps r = match r with
+    EMPTY -> Void
+  | ALT(r1, r2) -> 
+      if nullable r1 then Left(mkeps r1) else Right(mkeps r2)
+  | SEQ(r1, r2) -> Sequ(mkeps r1, mkeps r2)
+  | STAR(r) -> Stars([])
+  | RECD(x, r) -> Rec(x, mkeps r);;
+
+
+(* injection of a char into a value *)
+let rec inj r c v = match r, v with
+    STAR(r), Sequ(v1, Stars(vs)) -> Stars(inj r c v1 :: vs)
+  | SEQ(r1, r2), Sequ(v1, v2) -> Sequ(inj r1 c v1, v2)
+  | SEQ(r1, r2), Left(Sequ(v1, v2)) -> Sequ(inj r1 c v1, v2)
+  | SEQ(r1, r2), Right(v2) -> Sequ(mkeps r1, inj r2 c v2)
+  | ALT(r1, r2), Left(v1) -> Left(inj r1 c v1)
+  | ALT(r1, r2), Right(v2) -> Right(inj r2 c v2)
+  | CHAR(d), Void -> Chr(d) 
+  | RECD(x, r1), _ -> Rec(x, inj r1 c v);;
+
+(* some "rectification" functions for simplification *)
+let f_id v = v;;
+let f_right f = fun v -> Right(f v);;
+let f_left f = fun v -> Left(f v);;
+let f_alt f1 f2 = fun v -> match v with 
+    Right(v) -> Right(f2 v)
+  | Left(v) -> Left(f1 v);;
+let f_seq f1 f2 = fun v -> match v with 
+  Sequ(v1, v2) -> Sequ(f1 v1, f2 v2);;
+let f_seq_Void1 f1 f2 = fun v -> Sequ(f1 Void, f2 v);;
+let f_seq_Void2 f1 f2 = fun v -> Sequ(f1 v, f2 Void);;
+let f_rec f = fun v -> match v with
+    Rec(x, v) -> Rec(x, f v);;
+
+exception ShouldNotHappen
+let f_error v = raise ShouldNotHappen
+
+(* simplification of regular expressions returning also an 
+   rectification function; no simplification under STARs *)
+let rec simp r = match r with
+    ALT(r1, r2) -> 
+      let (r1s, f1s) = simp r1 in 
+      let (r2s, f2s) = simp r2 in
+      (match r1s, r2s with
+          NULL, _ -> (r2s, f_right f2s)
+        | _, NULL -> (r1s, f_left f1s)
+        | _, _    -> if r1s = r2s then (r1s, f_left f1s)
+                     else (ALT (r1s, r2s), f_alt f1s f2s)) 
+  | SEQ(r1, r2) -> 
+      let (r1s, f1s) = simp r1 in
+      let (r2s, f2s) = simp r2 in
+      (match r1s, r2s with
+          NULL, _  -> (NULL, f_error)
+        | _, NULL  -> (NULL, f_error)
+        | EMPTY, _ -> (r2s, f_seq_Void1 f1s f2s)
+        | _, EMPTY -> (r1s, f_seq_Void2 f1s f2s)
+        | _, _     -> (SEQ(r1s, r2s), f_seq f1s f2s))
+  | RECD(x, r1) -> 
+      let (r1s, f1s) = simp r1 in
+      (RECD(x, r1s), f_rec f1s)
+  | r -> (r, f_id)
+;;
+
+let rec der_simp c r = match r with
+    NULL -> (NULL, f_id)
+  | EMPTY -> (NULL, f_id)
+  | CHAR(d) -> ((if c = d then EMPTY else NULL), f_id)
+  | ALT(r1, r2) -> 
+      let (r1d, f1d) = der_simp c r1 in
+      let (r2d, f2d) = der_simp c r2 in
+      (match r1d, r2d with
+          NULL, _ -> (r2d, f_right f2d)
+        | _, NULL -> (r1d, f_left f1d)
+        | _, _    -> if r1d = r2d then (r1d, f_left f1d)
+                     else (ALT (r1d, r2d), f_alt f1d f2d))
+  | SEQ(r1, r2) -> 
+      if nullable r1 
+      then 
+        let (r1d, f1d) = der_simp c r1 in 
+        let (r2d, f2d) = der_simp c r2 in
+        let (r2s, f2s) = simp r2 in
+        (match r1d, r2s, r2d with
+            NULL, _, _  -> (r2d, f_right f2d)
+          | _, NULL, _  -> (r2d, f_right f2d)
+          | _, _, NULL  -> (SEQ(r1d, r2s), f_left (f_seq f1d f2s))
+          | EMPTY, _, _ -> (ALT(r2s, r2d), f_alt (f_seq_Void1 f1d f2s) f2d)
+          | _, EMPTY, _ -> (ALT(r1d, r2d), f_alt (f_seq_Void2 f1d f2s) f2d)
+          | _, _, _     -> (ALT(SEQ(r1d, r2s), r2d), f_alt (f_seq f1d f2s) f2d))
+      else 
+        let (r1d, f1d) = der_simp c r1 in
+        let (r2s, f2s) = simp r2 in
+        (match r1d, r2s with
+            NULL, _ -> (NULL, f_error)
+          | _, NULL -> (NULL, f_error)
+          | EMPTY, _ -> (r2s, f_seq_Void1 f1d f2s)
+          | _, EMPTY -> (r1d, f_seq_Void2 f1d f2s)
+          | _, _ -> (SEQ(r1d, r2s), f_seq f1d f2s))	  
+  | STAR(r1) -> 
+      let (r1d, f1d) = der_simp c r1 in
+      (match r1d with
+          NULL -> (NULL, f_error)
+        | EMPTY -> (STAR r1, f_seq_Void1 f1d f_id)
+        | _ -> (SEQ(r1d, STAR(r1)), f_seq f1d f_id))
+  | RECD(x, r1) -> der_simp c r1 
+
+
+(* matcher function *)
+let matcher r s = nullable(ders (explode s) r);;
+
+(* lexing function (produces a value) *)
+exception LexError;;
+
+let rec lex r s = match s with
+    [] -> if (nullable r) then mkeps r else raise LexError
+  | c::cs -> inj r c (lex (der c r) cs);;
+
+let lexing r s = lex r (explode s);;
+
+(* lexing with simplification *)
+let rec lex_simp r s = match s with
+    [] -> if (nullable r) then mkeps r else raise LexError
+  | c::cs -> 
+    let (r_simp, f_simp) = simp (der c r) in
+    inj r c (f_simp (lex_simp r_simp cs));;
+
+let lexing_simp r s = lex_simp r (explode s);;
+
+let rec lex_simp2 r s = match s with
+    [] -> if (nullable r) then mkeps r else raise LexError
+  | c::cs -> 
+    let (r_simp, f_simp) = der_simp c r in
+    inj r c (f_simp (lex_simp2 r_simp cs));;
+
+let lexing_simp2 r s = lex_simp2 r (explode s);;
+
+
+(* lexing with accumulation *)
+let rec lex_acc r s f = match s with
+    [] -> if (nullable r) then f (mkeps r) else raise LexError
+  | c::cs -> 
+    let (r_simp, f_simp) = simp (der c r) in
+    lex_acc r_simp cs (fun v -> f (inj r c (f_simp v)));;
+
+let lexing_acc r s = lex_acc r (explode s) (f_id);;
+
+let rec lex_acc2 r s f = match s with
+    [] -> if (nullable r) then f (mkeps r) else raise LexError
+  | c::cs -> 
+    let (r_simp, f_simp) = der_simp c r in
+    lex_acc2 r_simp cs (fun v -> f (inj r c (f_simp v)));;
+
+let lexing_acc2 r s = lex_acc2 r (explode s) (f_id);;
+
+
+(* Lexing rules for a small WHILE language *)
+let sym = alts (List.map chr (explode "abcdefghijklmnopqrstuvwxyz"));;
+let digit = alts (List.map chr (explode "0123456789"));;
+let idents =  sym -- STAR(sym ++ digit);;
+let nums = plus(digit);;
+let keywords = alts 
+   (List.map str ["skip"; "while"; "do"; "if"; "then"; "else"; "read"; "write"; "true"; "false"]);;
+let semicolon = str ";"
+let ops = alts 
+   (List.map str [":="; "=="; "-"; "+"; "*"; "!="; "<"; ">"; "<="; ">="; "%"; "/"]);;
+let whitespace = plus(str " " ++ str "\n" ++ str "\t");;
+let rparen = str ")";;
+let lparen = str "(";;
+let begin_paren = str "{";;
+let end_paren = str "}";;
+
+
+let while_regs = STAR(("k" $ keywords) ++
+                      ("i" $ idents) ++
+                      ("o" $ ops) ++ 
+                      ("n" $ nums) ++ 
+                      ("s" $ semicolon) ++ 
+                      ("p" $ (lparen ++ rparen)) ++ 
+                      ("b" $ (begin_paren ++ end_paren)) ++ 
+                      ("w" $ whitespace));;
+
+
+
+(* Some Tests
+  ============ *)
+
+let time f x =
+  let t = Sys.time() in
+  let f_x = (f x; f x; f x) in
+  (print_float ((Sys.time() -. t) /. 3.0); f_x);;
+
+
+let prog0 = "read n";;
+
+let prog1 = "read  n; write (n)";;
+string_of_env (env (lexing_simp while_regs prog1));;
+
+
+let prog2 = "
+i := 2;
+max := 100;
+while i < max do {
+  isprime := 1;
+  j := 2;
+  while (j * j) <= i + 1  do {
+    if i % j == 0 then isprime := 0  else skip;
+    j := j + 1
+  };
+  if isprime == 1 then write i else skip;
+  i := i + 1
+}";;
+
+let tst1 = (lexing_simp while_regs prog2 = lexing_simp2 while_regs prog2) in
+let tst2 = (lexing_simp while_regs prog2 = lexing_acc while_regs prog2) in
+let tst3 = (lexing_simp while_regs prog2 = lexing_acc2 while_regs prog2)
+in
+  print_string ("Sanity test simp vs simp2: >>" ^ (string_of_bool tst1) ^ "<<\n") ;
+  print_string ("Sanity test simp vs acc:   >>" ^ (string_of_bool tst2) ^ "<<\n") ;
+  print_string ("Sanity test simp vs acc2:  >>" ^ (string_of_bool tst3) ^ "<<") ;
+  print_newline ();;
+
+
+
+type range = 
+  To of int * int;;
+
+let (---) i j = To(i, j);; 
+
+let forby n =
+  fun range -> match range with To(lo, up) ->
+    (fun f -> 
+       let rec loop lo = 
+         if lo > up then () else (f lo; loop (lo + n))
+       in loop lo);;
+
+let step_simp i = 
+  (print_string ((string_of_int i) ^ ": ") ;
+   time (lexing_simp while_regs) (string_repeat prog2 i) ;
+   print_newline ());;
+
+let step_simp2 i = 
+  (print_string ((string_of_int i) ^ ": ") ;
+   time (lexing_simp2 while_regs) (string_repeat prog2 i) ;
+   print_newline ());;
+
+let step_acc i = 
+  (print_string ((string_of_int i) ^ ": ") ;
+   time (lexing_acc while_regs) (string_repeat prog2 i) ;
+   print_newline ());;
+
+let step_acc2 i = 
+  (print_string ((string_of_int i) ^ ": ") ;
+   time (lexing_acc2 while_regs) (string_repeat prog2 i) ;
+   print_newline ());;
+
+forby 100 (100 --- 700) step_simp;;
+print_newline ();;
+forby 100 (100 --- 700) step_simp2;;
+print_newline ();;
+forby 100 (100 --- 700) step_acc;;
+print_newline ();;
+forby 100 (100 --- 700) step_acc2;;
+print_newline ();;
+forby 1000 (1000 --- 5000) step_acc;;
+print_newline ();;
+forby 1000 (1000 --- 5000) step_acc2;;
+(*print_newline ();;*)
+(* forby 500 (100 --- 5000) step_simp;; *)
+