src/ast.sml

   1 (* HCoop Domtool (http://hcoop.sourceforge.net/)
   2  * Copyright (c) 2006-2007, Adam Chlipala
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  17  *)
  18
  19 (* Configuration language abstract syntax *)
  20
  21 structure Ast = struct
  22
  23 open DataStructures
  24
  25 (* A description of a predicate on configuration block stacks *)
  26 datatype pred' =
  27          CRoot
  28        (* The stack is empty. *)
  29        | CConst of string
  30        (* The given pred name is on top of the stack. *)
  31        | CPrefix of pred
  32        (* Some prefix of the stack matches the pred. *)
  33        | CNot of pred
  34        (* The pred does not match. *)
  35        | CAnd of pred * pred
  36        (* Both preds match. *)
  37 withtype pred = pred' * position
  38
  39 datatype typ' =
  40          TBase of string
  41        (* Base type *)
  42        | TList of typ
  43        (* SML 'a list *)
  44        | TArrow of typ * typ
  45        (* SML -> *)
  46        | TAction of pred * record * record
  47        (* An action that:
  48         *  - Is valid in the given pred
  49         *  - Expects an environment compatible with the first record
  50         *  - Modifies it according to the second record *)
  51        | TNested of pred * typ
  52        (* Allow nested configuration, in the form of a function from an action
  53         * satisfying the first predicate to an action satisfying the second and
  54         * with the same environment variable IO behavior. *)
  55
  56        | TError
  57        (* Marker that something already went wrong, so don't generate further
  58         * error messages. *)
  59        | TUnif of string * typ option ref
  60        (* Unification variable to be determined during type-checking *)
  61 withtype typ = typ' * position
  62      and record = (typ' * position) StringMap.map
  63
  64 datatype exp' =
  65          EInt of int
  66        (* Constant integer *)
  67        | EString of string
  68        (* Constant string *)
  69        | EList of exp list
  70        (* Basic list constructor *)
  71
  72        | ELam of string * typ option * exp
  73        (* Function abstraction *)
  74        | EVar of string
  75        (* Variable bound by a function *)
  76        | EApp of exp * exp
  77        (* Function application *)
  78
  79        | ESkip
  80        (* Do-nothing action *)
  81        | ESet of string * exp
  82        (* Set an environment variable *)
  83        | EGet of string * typ option * string * exp
  84        (* Get an environment variable *)
  85        | ESeq of exp list
  86        (* Monad sequencer; execute a number of commands in order *)
  87        | ELocal of exp * exp
  88        (* Local execution; like ESeq, but the writes of the first
  89         * action are abandoned *)
  90        | EWith of exp * exp
  91        (* Apply a TNested to an action *)
  92        | EALam of string * pred * exp
  93        (* Abstraction for building TNested values *)
  94        | EIf of exp * exp * exp
  95        (* If..then..else *)
  96 withtype exp = exp' * position
  97
  98 datatype decl' =
  99          DExternType of string
 100        | DExternVal of string * typ
 101        | DVal of string * typ option * exp
 102        | DContext of string
 103 type decl = decl' * string option * position
 104
 105 type file = string option * decl list * exp option
 106
 107 fun multiApp (f, loc, args) =
 108     foldl (fn (arg, e) => (EApp (e, arg), loc)) f args
 109
 110 datatype unification_error =
 111          UnifyPred of pred * pred
 112        | UnifyTyp of typ * typ
 113        | UnifyOccurs of string * typ
 114
 115 exception Unify of unification_error
 116
 117 datatype type_error =
 118          WrongType of string * exp * typ * typ * unification_error option
 119        | WrongForm of string * string * exp * typ * unification_error option
 120        | UnboundVariable of string
 121        | WrongPred of string * pred * pred
 122
 123 end