/
fvec.sml
81 lines (60 loc) · 1.68 KB
/
fvec.sml
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(* Fusable vectors *)
structure Fvec :> VEC = struct
type 'a t = int * (int -> 'a)
fun fromList (l:'a list) : 'a t =
let val a = Vector.fromList l
in (Vector.length a, fn i => Vector.sub(a,i))
end
fun map f (n,g) = (n, f o g)
fun fmap a v = map (fn f => f v) a
fun iter (n,e,f) =
let fun loop (i,a) =
if i >= n then a
else loop (i+1, f(i,a))
in loop(0,e)
end
fun iter' (n,e,f) =
let fun loop (i,a) =
if i <= 0 then a
else let val i2 = i-1
in loop (i2, f(i2,a))
end
in loop(n,e)
end
fun foldl f e (n,g) = iter(n,e, fn (i,a) => f(g i,a))
fun foldr f e (n,g) = iter'(n,e, fn (i,a) => f(g i,a))
fun emp _ = raise Fail "impossible"
fun empty () = (0, emp)
fun tk n (a as (m,g)) =
if n >= m then a
else (n,g)
fun dr n (m,g) =
if n >= m then empty()
else (m-n,fn i => g(i+n))
fun tabulate n f = (n,f)
fun list a = foldr (op ::) nil a
fun length (n,_) = n
fun map2 f (n1,f1) (n2,f2) =
if n1 <> n2 then raise Fail "map2 applied to vectors of different lengths"
else (n1,fn i => f(f1 i)(f2 i))
fun single x = fromList [x]
fun eq beq (a1,a2) =
length a1 = length a2 andalso
(foldl(fn (x,a) => x andalso a) true
(map2 (fn x => fn y => beq(x,y)) a1 a2))
fun concat (n1,f1) (n2,f2) =
(n1+n2, fn i => if i < n1 then f1 i else f2 (i-n1))
fun flatten v =
let val len = foldl (fn (a,l) => length a + l) 0 v
val f = foldr (fn ((n,f),g) =>
fn i => if i < n then f i else g (i-n)) emp v
in (len,f)
end
fun sub ((n,f),i) =
if i > n-1 orelse i < 0 then raise Subscript
else f i
fun memoize (n,f) =
let val v = Vector.tabulate(n,f)
in (n, fn i => Vector.sub(v,i))
end
end