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(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2015 *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(************************************************************************)
(** This file defines the low-level monadic operations used by the
tactic monad. The monad is divided into two layers: a non-logical
layer which consists in operations which will not (or cannot) be
backtracked in case of failure (input/output or persistent state)
and a logical layer which handles backtracking, proof
manipulation, and any other effect which needs to backtrack. *)
(** {6 Exceptions} *)
(** To help distinguish between exceptions raised by the IO monad from
the one used natively by Coq, the former are wrapped in
[Exception]. It is only used internally so that [catch] blocks of
the IO monad would only catch exceptions raised by the [raise]
function of the IO monad, and not for instance, by system
interrupts. Also used in [Proofview] to avoid capturing exception
from the IO monad ([Proofview] catches errors in its compatibility
layer, and when lifting goal-level expressions). *)
exception Exception of exn
(** This exception is used to signal abortion in [timeout] functions. *)
exception Timeout
(** This exception is used by the tactics to signal failure by lack of
successes, rather than some other exceptions (like system
interrupts). *)
exception TacticFailure of exn
(** {6 Non-logical layer} *)
(** The non-logical monad is a simple [unit -> 'a] (i/o) monad. The
operations are simple wrappers around corresponding usual
operations and require little documentation. *)
module NonLogical : sig
include Monad.S
val ignore : 'a t -> unit t
type 'a ref
val ref : 'a -> 'a ref t
(** [Pervasives.(:=)] *)
val (:=) : 'a ref -> 'a -> unit t
(** [Pervasives.(!)] *)
val (!) : 'a ref -> 'a t
val read_line : string t
val print_char : char -> unit t
(** {!Pp.pp}. The buffer is also flushed. *)
val print : Pp.std_ppcmds -> unit t
(** [Pervasives.raise]. Except that exceptions are wrapped with
{!Exception}. *)
val raise : ?info:Exninfo.info -> exn -> 'a t
(** [try ... with ...] but restricted to {!Exception}. *)
val catch : 'a t -> (Exninfo.iexn -> 'a t) -> 'a t
val timeout : int -> 'a t -> 'a t
(** Construct a monadified side-effect. Exceptions raised by the argument are
wrapped with {!Exception}. *)
val make : (unit -> 'a) -> 'a t
(** [run] performs effects. *)
val run : 'a t -> 'a
end
(** {6 Logical layer} *)
(** The logical monad is a backtracking monad on top of which is
layered a state monad (which is used to implement all of read/write,
read only, and write only effects). The state monad being layered on
top of the backtracking monad makes it so that the state is
backtracked on failure.
Backtracking differs from regular exception in that, writing (+)
for exception catching and (>>=) for bind, we require the
following extra distributivity laws:
x+(y+z) = (x+y)+z
zero+x = x
x+zero = x
(x+y)>>=k = (x>>=k)+(y>>=k) *)
(** A view type for the logical monad, which is a form of list, hence
we can decompose it with as a list. *)
type ('a, 'b) list_view =
| Nil of Exninfo.iexn
| Cons of 'a * 'b
(** The monad is parametrised in the types of state, environment and
writer. *)
module type Param = sig
(** Read only *)
type e
(** Write only *)
type w
(** [w] must be a monoid *)
val wunit : w
val wprod : w -> w -> w
(** Read-write *)
type s
(** Update-only. Essentially a writer on [u->u]. *)
type u
(** [u] must be pointed. *)
val uunit : u
end
module Logical (P:Param) : sig
include Monad.S
val ignore : 'a t -> unit t
val set : P.s -> unit t
val get : P.s t
val modify : (P.s -> P.s) -> unit t
val put : P.w -> unit t
val current : P.e t
val local : P.e -> 'a t -> 'a t
val update : (P.u -> P.u) -> unit t
val zero : Exninfo.iexn -> 'a t
val plus : 'a t -> (Exninfo.iexn -> 'a t) -> 'a t
val split : 'a t -> (('a,(Exninfo.iexn->'a t)) list_view) t
val once : 'a t -> 'a t
val break : (Exninfo.iexn -> Exninfo.iexn option) -> 'a t -> 'a t
val lift : 'a NonLogical.t -> 'a t
type 'a reified
val repr : 'a reified -> ('a, Exninfo.iexn -> 'a reified) list_view NonLogical.t
val run : 'a t -> P.e -> P.s -> ('a * P.s * P.w * P.u) reified
end
|
