Please take a guess.
Which of the following three is the fastest?
(* ****** ****** *)
//
fun
{a:t0p}
gfact1(n: int): a = let
//
overload * with gmul_int_val
//
in
//
(fix
f( i: int
, n: int, r: a): a =>
if i < n
then f(i+1, n, (i+1)*r) else r
// end of [if]
)(0, n, gnumber_int<a>(1))
//
end // end of [let] // end of [gfact1]
//
(* ****** ****** *)
fun
{a:t0p}
gfact2(n: int): a = let
//
overload * with gmul_int_val
//
fun
loop
(xs: stream_vt(int), r0: a): a =
(
case+ !xs of
| ~stream_vt_nil
() => r0
| ~stream_vt_cons
(x0, xs) => loop(xs, (x0+1)*r0)
)
//
val _0_n_ =
streamize_intrange_lr<>(0, n)
//
in
loop(_0_n_, gnumber_int<a>(1))
end // end of [let] // end of [gfact2]
(* ****** ****** *)
fun
{a:t0p}
product
(xs: stream_vt(a)): a = let
//
overload * with gmul_val_val
//
fun
loop
(xs: stream_vt(a), r0: a): a =
(
case+ !xs of
| ~stream_vt_nil() => r0
| ~stream_vt_cons(x0, xs) => loop(xs, r0*x0)
)
//
in
loop(xs, gnumber_int<a>(1))
end // end of [product]
fun
{a:t0p}
gfact3(n: int): a =
product<a>
(stream_vt_map_cloptr
(streamize_intrange_lr<>(0, n), lam(i) => gnumber_int<a>(i+1))
) (* end of [gfact3] *)
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