src/Pure/primitive_defs.ML
author wenzelm
Fri May 28 20:41:23 2010 +0200 (2010-05-28)
changeset 37174 6feaab4fc27d
parent 35989 3418cdf1855e
child 42284 326f57825e1a
permissions -rw-r--r--
assume given SCALA_HOME, e.g. from component settings or external setup;
     1 (*  Title:      Pure/primitive_defs.ML
     2     Author:     Makarius
     3 
     4 Primitive definition forms.
     5 *)
     6 
     7 signature PRIMITIVE_DEFS =
     8 sig
     9   val dest_def: Proof.context -> (term -> bool) -> (string -> bool) -> (string -> bool) ->
    10     term -> (term * term) * term
    11   val abs_def: term -> term * term
    12 end;
    13 
    14 structure Primitive_Defs: PRIMITIVE_DEFS =
    15 struct
    16 
    17 fun term_kind (Const _) = "existing constant "
    18   | term_kind (Free _) = "free variable "
    19   | term_kind (Bound _) = "bound variable "
    20   | term_kind _ = "";
    21 
    22 (*c x == t[x] to !!x. c x == t[x]*)
    23 fun dest_def ctxt check_head is_fixed is_fixedT eq =
    24   let
    25     fun err msg = raise TERM (msg, [eq]);
    26     val eq_vars = Term.strip_all_vars eq;
    27     val eq_body = Term.strip_all_body eq;
    28 
    29     val display_terms =
    30       commas_quote o map (Syntax.string_of_term ctxt o Syntax.bound_vars eq_vars);
    31     val display_types = commas_quote o map (Syntax.string_of_typ ctxt);
    32 
    33     val (raw_lhs, rhs) = Logic.dest_equals eq_body handle TERM _ => err "Not a meta-equality (==)";
    34     val lhs = Envir.beta_eta_contract raw_lhs;
    35     val (head, args) = Term.strip_comb lhs;
    36     val head_tfrees = Term.add_tfrees head [];
    37 
    38     fun check_arg (Bound _) = true
    39       | check_arg (Free (x, _)) = not (is_fixed x)
    40       | check_arg (Const ("TYPE", Type ("itself", [TFree _]))) = true
    41       | check_arg _ = false;
    42     fun close_arg (Bound _) t = t
    43       | close_arg x t = Term.all (Term.fastype_of x) $ lambda x t;
    44 
    45     val lhs_bads = filter_out check_arg args;
    46     val lhs_dups = duplicates (op aconv) args;
    47     val rhs_extras = Term.fold_aterms (fn v as Free (x, _) =>
    48       if is_fixed x orelse member (op aconv) args v then I
    49       else insert (op aconv) v | _ => I) rhs [];
    50     val rhs_extrasT = Term.fold_aterms (Term.fold_types (fn v as TFree (a, S) =>
    51       if is_fixedT a orelse member (op =) head_tfrees (a, S) then I
    52       else insert (op =) v | _ => I)) rhs [];
    53   in
    54     if not (check_head head) then
    55       err ("Bad head of lhs: " ^ term_kind head ^ display_terms [head])
    56     else if not (null lhs_bads) then
    57       err ("Bad arguments on lhs: " ^ display_terms lhs_bads)
    58     else if not (null lhs_dups) then
    59       err ("Duplicate arguments on lhs: " ^ display_terms lhs_dups)
    60     else if not (null rhs_extras) then
    61       err ("Extra variables on rhs: " ^ display_terms rhs_extras)
    62     else if not (null rhs_extrasT) then
    63       err ("Extra type variables on rhs: " ^ display_types rhs_extrasT)
    64     else if exists_subterm (fn t => t aconv head) rhs then
    65       err "Entity to be defined occurs on rhs"
    66     else
    67       ((lhs, rhs), fold_rev close_arg args (Term.list_all (eq_vars, (Logic.mk_equals (lhs, rhs)))))
    68   end;
    69 
    70 (*!!x. c x == t[x] to c == %x. t[x]*)
    71 fun abs_def eq =
    72   let
    73     val body = Term.strip_all_body eq;
    74     val vars = map Free (Term.rename_wrt_term body (Term.strip_all_vars eq));
    75     val (lhs, rhs) = Logic.dest_equals (Term.subst_bounds (vars, body));
    76     val (lhs', args) = Term.strip_comb lhs;
    77     val rhs' = Term.list_abs_free (map Term.dest_Free args, rhs);
    78   in (lhs', rhs') end;
    79 
    80 end;