TFL/utils.sml
 author wenzelm Wed, 25 Aug 1999 20:49:02 +0200 changeset 7357 d0e16da40ea2 parent 3391 5e45dd3b64e9 child 9867 bf8300fa4238 permissions -rw-r--r--
proper bootstrap of HOL theory and packages;
```
(*  Title:      TFL/utils
ID:         \$Id\$
Author:     Konrad Slind, Cambridge University Computer Laboratory

Basic utilities
*)

structure Utils =
struct

(* Standard exception for TFL. *)
exception ERR of {module:string,func:string, mesg:string};
fun UTILS_ERR{func,mesg} = ERR{module = "Utils",func=func,mesg=mesg};

(* Simple combinators *)

fun C f x y = f y x

fun itlist f L base_value =
let fun it [] = base_value
| it (a::rst) = f a (it rst)
in it L
end;

fun rev_itlist f =
let fun rev_it [] base = base
| rev_it (a::rst) base = rev_it rst (f a base)
in rev_it
end;

fun end_itlist f =
let fun endit [] = raise UTILS_ERR{func="end_itlist", mesg="list too short"}
| endit alist =
let val (base::ralist) = rev alist
in itlist f (rev ralist) base
end
in endit
end;

fun itlist2 f L1 L2 base_value =
let fun it ([],[]) = base_value
| it ((a::rst1),(b::rst2)) = f a b (it (rst1,rst2))
| it _ = raise UTILS_ERR{func="itlist2",mesg="different length lists"}
in  it (L1,L2)
end;

fun pluck p  =
| remv (h::t, A) = if p h then (h, rev A @ t) else remv (t,h::A)
in fn L => remv(L,[])
end;

fun take f =
let fun grab(0,L) = []
| grab(n, x::rst) = f x::grab(n-1,rst)
in grab
end;

fun zip3 [][][] = []
| zip3 (x::l1) (y::l2) (z::l3) = (x,y,z)::zip3 l1 l2 l3
| zip3 _ _ _ = raise UTILS_ERR{func="zip3",mesg="different lengths"};

fun can f x = (f x ; true) handle _ => false;
fun holds P x = P x handle _ => false;

fun sort R =
let fun part (m, []) = ([],[])
| part (m, h::rst) =
let val (l1,l2) = part (m,rst)
in if (R h m) then (h::l1, l2)
else (l1,  h::l2) end
fun qsort [] = []
| qsort (h::rst) =
let val (l1,l2) = part(h,rst)
in qsort l1@ [h] @qsort l2
end
in qsort
end;

end; (* Utils *)
```