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(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2010 *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(************************************************************************)
(** Extraction of [positive], [N] and [Z] into Ocaml's [int] *)
Require Import ZArith NArith.
Require Import ExtrOcamlBasic.
(** Disclaimer: trying to obtain efficient certified programs
by extracting [Z] into [int] is definitively *not* a good idea.
See the Disclaimer in [ExtrOcamlNatInt]. *)
(** Mapping of [positive], [Z], [N] into [int]. The last strings
emulate the matching, see documentation of [Extract Inductive]. *)
Extract Inductive positive => int
[ "(fun p->1+2*p)" "(fun p->2*p)" "1" ]
"(fun f2p1 f2p f1 p ->
if p<=1 then f1 () else if p mod 2 = 0 then f2p (p/2) else f2p1 (p/2))".
Extract Inductive Z => int [ "0" "" "(~-)" ]
"(fun f0 fp fn z -> if z=0 then f0 () else if z>0 then fp z else fn (-z))".
Extract Inductive N => int [ "0" "" ]
"(fun f0 fp n -> if n=0 then f0 () else fp n)".
(** Nota: the "" above is used as an identity function "(fun p->p)" *)
(** Efficient (but uncertified) versions for usual functions *)
Extract Constant Pos.add => "(+)".
Extract Constant Pos.succ => "succ".
Extract Constant Pos.pred => "fun n -> max 1 (n-1)".
Extract Constant Pos.sub => "fun n m -> max 1 (n-m)".
Extract Constant Pos.mul => "( * )".
Extract Constant Pos.min => "min".
Extract Constant Pos.max => "max".
Extract Constant Pos.compare =>
"fun x y -> if x=y then Eq else if x<y then Lt else Gt".
Extract Constant Pos.compare_cont =>
"fun x y c -> if x=y then c else if x<y then Lt else Gt".
Extract Constant N.add => "(+)".
Extract Constant N.succ => "succ".
Extract Constant N.pred => "fun n -> max 0 (n-1)".
Extract Constant N.sub => "fun n m -> max 0 (n-m)".
Extract Constant N.mul => "( * )".
Extract Constant N.min => "min".
Extract Constant N.max => "max".
Extract Constant N.div => "fun a b -> if b=0 then 0 else a/b".
Extract Constant N.modulo => "fun a b -> if b=0 then a else a mod b".
Extract Constant N.compare =>
"fun x y -> if x=y then Eq else if x<y then Lt else Gt".
Extract Constant Z.add => "(+)".
Extract Constant Z.succ => "succ".
Extract Constant Z.pred => "pred".
Extract Constant Z.sub => "(-)".
Extract Constant Z.mul => "( * )".
Extract Constant Z.opp => "(~-)".
Extract Constant Z.abs => "abs".
Extract Constant Z.min => "min".
Extract Constant Z.max => "max".
Extract Constant Z.compare =>
"fun x y -> if x=y then Eq else if x<y then Lt else Gt".
Extract Constant Z.of_N => "fun p -> p".
Extract Constant Z.abs_N => "abs".
(** Zdiv and Zmod are quite complex to define in terms of (/) and (mod).
For the moment we don't even try *)
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