Deleted Library.option type.
signature LAZY_SEQ =
sig
type 'a seq
(* From LIST *)
val null : 'a seq -> bool
val length : 'a seq -> int
val @ : 'a seq * 'a seq -> 'a seq
val hd : 'a seq -> 'a
val tl : 'a seq -> 'a seq
val last : 'a seq -> 'a
val getItem : 'a seq -> ('a * 'a seq) option
val nth : 'a seq * int -> 'a
val take : 'a seq * int -> 'a seq
val drop : 'a seq * int -> 'a seq
val rev : 'a seq -> 'a seq
val concat : 'a seq seq -> 'a seq
val revAppend : 'a seq * 'a seq -> 'a seq
val app : ('a -> unit) -> 'a seq -> unit
val map : ('a -> 'b) -> 'a seq -> 'b seq
val mapPartial : ('a -> 'b option) -> 'a seq -> 'b seq
val find : ('a -> bool) -> 'a seq -> 'a option
val filter : ('a -> bool) -> 'a seq -> 'a seq
val partition : ('a -> bool)
-> 'a seq -> 'a seq * 'a seq
val foldl : ('a * 'b -> 'b) -> 'b -> 'a seq -> 'b
val foldr : ('a * 'b -> 'b) -> 'b -> 'a seq -> 'b
val exists : ('a -> bool) -> 'a seq -> bool
val all : ('a -> bool) -> 'a seq -> bool
val tabulate : int * (int -> 'a) -> 'a seq
val collate : ('a * 'a -> order)
-> 'a seq * 'a seq -> order
(* Miscellaneous *)
val cycle : ((unit ->'a seq) -> 'a seq) -> 'a seq
val iterates : ('a -> 'a) -> 'a -> 'a seq
val of_function: (unit -> 'a option) -> 'a seq
val of_string : string -> char seq
val of_instream: TextIO.instream -> char seq
(* From SEQ *)
val make: (unit -> ('a * 'a seq) option) -> 'a seq
val empty: 'a -> 'a seq
val cons: 'a * 'a seq -> 'a seq
val single: 'a -> 'a seq
val try: ('a -> 'b) -> 'a -> 'b seq
val chop: int * 'a seq -> 'a list * 'a seq
val list_of: 'a seq -> 'a list
val of_list: 'a list -> 'a seq
val mapp: ('a -> 'b) -> 'a seq -> 'b seq -> 'b seq
val interleave: 'a seq * 'a seq -> 'a seq
val print: (int -> 'a -> unit) -> int -> 'a seq -> unit
val it_right : ('a * 'b seq -> 'b seq) -> 'a seq * 'b seq -> 'b seq
val commute: 'a seq list -> 'a list seq
val succeed: 'a -> 'a seq
val fail: 'a -> 'b seq
val THEN: ('a -> 'b seq) * ('b -> 'c seq) -> 'a -> 'c seq
val ORELSE: ('a -> 'b seq) * ('a -> 'b seq) -> 'a -> 'b seq
val APPEND: ('a -> 'b seq) * ('a -> 'b seq) -> 'a -> 'b seq
val EVERY: ('a -> 'a seq) list -> 'a -> 'a seq
val FIRST: ('a -> 'b seq) list -> 'a -> 'b seq
val TRY: ('a -> 'a seq) -> 'a -> 'a seq
val REPEAT: ('a -> 'a seq) -> 'a -> 'a seq
val REPEAT1: ('a -> 'a seq) -> 'a -> 'a seq
val INTERVAL: (int -> 'a -> 'a seq) -> int -> int -> 'a -> 'a seq
val DETERM: ('a -> 'b seq) -> 'a -> 'b seq
end
structure LazySeq :> LAZY_SEQ =
struct
open Susp
datatype 'a seq = Seq of ('a * 'a seq) option susp
exception Empty
fun getItem (Seq s) = force s
fun make f = Seq (delay f)
fun null s = is_some (getItem s)
local
fun F n NONE = n
| F n (SOME(_,s)) = F (n+1) (getItem s)
in
fun length s = F 0 (getItem s)
end
fun s1 @ s2 =
let
fun F NONE = getItem s2
| F (SOME(x,s1')) = SOME(x,F' s1')
and F' s = make (fn () => F (getItem s))
in
F' s1
end
local
fun F NONE = raise Empty
| F (SOME arg) = arg
in
fun hd s = #1 (F (getItem s))
fun tl s = #2 (F (getItem s))
end
local
fun F x NONE = x
| F _ (SOME(x,s)) = F x (getItem s)
fun G NONE = raise Empty
| G (SOME(x,s)) = F x (getItem s)
in
fun last s = G (getItem s)
end
local
fun F NONE _ = raise Subscript
| F (SOME(x,_)) 0 = x
| F (SOME(_,s)) n = F (getItem s) (n-1)
in
fun nth(s,n) =
if n < 0
then raise Subscript
else F (getItem s) n
end
local
fun F NONE _ = raise Subscript
| F (SOME(x,s)) n = SOME(x,F' s (n-1))
and F' s 0 = Seq (value NONE)
| F' s n = make (fn () => F (getItem s) n)
in
fun take (s,n) =
if n < 0
then raise Subscript
else F' s n
end
local
fun F s 0 = s
| F NONE _ = raise Subscript
| F (SOME(_,s)) n = F (getItem s) (n-1)
in
fun drop (s,0) = s
| drop (s,n) =
if n < 0
then raise Subscript
else make (fn () => F (getItem s) n)
end
local
fun F s NONE = s
| F s (SOME(x,s')) = F (SOME(x, Seq (value s))) (getItem s')
in
fun rev s = make (fn () => F NONE (getItem s))
end
local
fun F s NONE = getItem s
| F s (SOME(x,s')) = F (Seq (value (SOME(x,s)))) (getItem s')
in
fun revAppend (s1,s2) = make (fn () => F s2 (getItem s1))
end
local
fun F NONE = NONE
| F (SOME(s1,s2)) =
let
fun G NONE = F (getItem s2)
| G (SOME(x,s)) = SOME(x,make (fn () => G (getItem s)))
in
G (getItem s1)
end
in
fun concat s = make (fn () => F (getItem s))
end
fun app f =
let
fun F NONE = ()
| F (SOME(x,s)) =
(f x;
F (getItem s))
in
F o getItem
end
fun map f =
let
fun F NONE = NONE
| F (SOME(x,s)) = SOME(f x,F' s)
and F' s = make (fn() => F (getItem s))
in
F'
end
fun mapPartial f =
let
fun F NONE = NONE
| F (SOME(x,s)) =
(case f x of
SOME y => SOME(y,F' s)
| NONE => F (getItem s))
and F' s = make (fn()=> F (getItem s))
in
F'
end
fun find P =
let
fun F NONE = NONE
| F (SOME(x,s)) =
if P x
then SOME x
else F (getItem s)
in
F o getItem
end
(*fun filter p = mapPartial (fn x => if p x then SOME x else NONE)*)
fun filter P =
let
fun F NONE = NONE
| F (SOME(x,s)) =
if P x
then SOME(x,F' s)
else F (getItem s)
and F' s = make (fn () => F (getItem s))
in
F'
end
fun partition f s =
let
val s' = map (fn x => (x,f x)) s
in
(mapPartial (fn (x,true) => SOME x | _ => NONE) s',
mapPartial (fn (x,false) => SOME x | _ => NONE) s')
end
fun exists P =
let
fun F NONE = false
| F (SOME(x,s)) = P x orelse F (getItem s)
in
F o getItem
end
fun all P =
let
fun F NONE = true
| F (SOME(x,s)) = P x andalso F (getItem s)
in
F o getItem
end
(*fun tabulate f = map f (iterates (fn x => x + 1) 0)*)
fun tabulate (n,f) =
let
fun F n = make (fn () => SOME(f n,F (n+1)))
in
F n
end
fun collate c (s1,s2) =
let
fun F NONE _ = LESS
| F _ NONE = GREATER
| F (SOME(x,s1)) (SOME(y,s2)) =
(case c (x,y) of
LESS => LESS
| GREATER => GREATER
| EQUAL => F' s1 s2)
and F' s1 s2 = F (getItem s1) (getItem s2)
in
F' s1 s2
end
fun empty _ = Seq (value NONE)
fun single x = Seq(value (SOME(x,Seq (value NONE))))
fun cons a = Seq(value (SOME a))
fun cycle seqfn =
let
val knot = ref (Seq (value NONE))
in
knot := seqfn (fn () => !knot);
!knot
end
fun iterates f =
let
fun F x = make (fn() => SOME(x,F (f x)))
in
F
end
fun interleave (s1,s2) =
let
fun F NONE = getItem s2
| F (SOME(x,s1')) = SOME(x,interleave(s2,s1'))
in
make (fn()=> F (getItem s1))
end
(* val force_all = app ignore *)
local
fun F NONE = ()
| F (SOME(x,s)) = F (getItem s)
in
fun force_all s = F (getItem s)
end
fun of_function f =
let
fun F () = case f () of
SOME x => SOME(x,make F)
| NONE => NONE
in
make F
end
local
fun F [] = NONE
| F (x::xs) = SOME(x,F' xs)
and F' xs = make (fn () => F xs)
in
fun of_list xs = F' xs
end
val of_string = of_list o String.explode
fun of_instream is =
let
val buffer : char list ref = ref []
fun get_input () =
case !buffer of
(c::cs) => (buffer:=cs;
SOME c)
| [] => (case String.explode (TextIO.input is) of
[] => NONE
| (c::cs) => (buffer := cs;
SOME c))
in
of_function get_input
end
local
fun F k NONE = k []
| F k (SOME(x,s)) = F (fn xs => k (x::xs)) (getItem s)
in
fun list_of s = F (fn x => x) (getItem s)
end
(* Adapted from seq.ML *)
val succeed = single
fun fail _ = Seq (value NONE)
(* fun op THEN (f, g) x = flat (map g (f x)) *)
fun op THEN (f, g) =
let
fun F NONE = NONE
| F (SOME(x,xs)) =
let
fun G NONE = F (getItem xs)
| G (SOME(y,ys)) = SOME(y,make (fn () => G (getItem ys)))
in
G (getItem (g x))
end
in
fn x => make (fn () => F (getItem (f x)))
end
fun op ORELSE (f, g) x =
make (fn () =>
case getItem (f x) of
NONE => getItem (g x)
| some => some)
fun op APPEND (f, g) x =
let
fun copy s =
case getItem s of
NONE => getItem (g x)
| SOME(x,xs) => SOME(x,make (fn () => copy xs))
in
make (fn () => copy (f x))
end
fun EVERY fs = foldr THEN (fs, succeed)
fun FIRST fs = foldr ORELSE (fs, fail)
fun TRY f x =
make (fn () =>
case getItem (f x) of
NONE => SOME(x,Seq (value NONE))
| some => some)
fun REPEAT f =
let
fun rep qs x =
case getItem (f x) of
NONE => SOME(x, make (fn () => repq qs))
| SOME (x', q) => rep (q :: qs) x'
and repq [] = NONE
| repq (q :: qs) =
case getItem q of
NONE => repq qs
| SOME (x, q) => rep (q :: qs) x
in
fn x => make (fn () => rep [] x)
end
fun REPEAT1 f = THEN (f, REPEAT f);
fun INTERVAL f i =
let
fun F j =
if i > j
then single
else op THEN (f j, F (j - 1))
in F end
fun DETERM f x =
make (fn () =>
case getItem (f x) of
NONE => NONE
| SOME (x', _) => SOME(x',Seq (value NONE)))
(*partial function as procedure*)
fun try f x =
make (fn () =>
case Library.try f x of
SOME y => SOME(y,Seq (value NONE))
| NONE => NONE)
(*functional to print a sequence, up to "count" elements;
the function prelem should print the element number and also the element*)
fun print prelem count seq =
let
fun pr k xq =
if k > count
then ()
else
case getItem xq of
NONE => ()
| SOME (x, xq') =>
(prelem k x;
writeln "";
pr (k + 1) xq')
in
pr 1 seq
end
(*accumulating a function over a sequence; this is lazy*)
fun it_right f (xq, yq) =
let
fun its s =
make (fn () =>
case getItem s of
NONE => getItem yq
| SOME (a, s') => getItem(f (a, its s')))
in
its xq
end
(*map over a sequence s1, append the sequence s2*)
fun mapp f s1 s2 =
let
fun F NONE = getItem s2
| F (SOME(x,s1')) = SOME(f x,F' s1')
and F' s = make (fn () => F (getItem s))
in
F' s1
end
(*turn a list of sequences into a sequence of lists*)
local
fun F [] = SOME([],Seq (value NONE))
| F (xq :: xqs) =
case getItem xq of
NONE => NONE
| SOME (x, xq') =>
(case F xqs of
NONE => NONE
| SOME (xs, xsq) =>
let
fun G s =
make (fn () =>
case getItem s of
NONE => F (xq' :: xqs)
| SOME(ys,ysq) => SOME(x::ys,G ysq))
in
SOME (x :: xs, G xsq)
end)
in
fun commute xqs = make (fn () => F xqs)
end
(*the list of the first n elements, paired with rest of sequence;
if length of list is less than n, then sequence had less than n elements*)
fun chop (n, xq) =
if n <= 0
then ([], xq)
else
case getItem xq of
NONE => ([], xq)
| SOME (x, xq') => apfst (Library.cons x) (chop (n - 1, xq'))
fun foldl f e s =
let
fun F k NONE = k e
| F k (SOME(x,s)) = F (fn y => k (f(x,y))) (getItem s)
in
F (fn x => x) (getItem s)
end
fun foldr f e s =
let
fun F e NONE = e
| F e (SOME(x,s)) = F (f(x,e)) (getItem s)
in
F e (getItem s)
end
end