-
-
Save Kraks/05a4799dea5e812ad8ebba26d7b7a87d to your computer and use it in GitHub Desktop.
Staged Fixed-point combinator
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| open Microsoft.FSharp.Quotations | |
| // <@ fun x -> (% <@ x @> ) @> ~ lambda (fun x -> x) | |
| let lambda (f : Expr<'T> -> Expr<'R>) : Expr<'T -> 'R> = | |
| let var = new Var("__temp__", typeof<'T>) | |
| Expr.Cast<_>(Expr.Lambda(var, f (Expr.Cast<_>(Expr.Var var)))) | |
| // fixed-point combinator | |
| let rec fix : (('Τ -> 'R) -> ('Τ -> 'R)) -> 'Τ -> 'R = fun f x -> | |
| f (fix f) x | |
| let power x f = | |
| fun n -> | |
| match n with | |
| | 0 -> <@ 1 @> | |
| | n -> <@ %x * (% f (n - 1) ) @> | |
| let power2 = fix (power <@ 2 @>) | |
| power2 10 // loop unroll 10 times | |
| // Staged fixed-point combinator | |
| let fix' : (Expr<'T -> 'R> -> Expr<'T -> 'R>) -> Expr<'T -> 'R> = fun f -> | |
| <@ fun x -> let rec loop x = (% lambda (fun f' -> f f') ) loop x in loop x @> | |
| let power' x f = | |
| <@ fun n -> | |
| match n with | |
| | 0 -> 1 | |
| | n -> %x * (%f) (n - 1) @> | |
| let power2' = fix' (power' <@ 2 @>) |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment