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(* Title: HOL/Tools/legacy_monomorph.ML
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Author: Sascha Boehme, TU Muenchen
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Monomorphization of theorems, i.e., computation of all (necessary)
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instances. This procedure is incomplete in general, but works well for
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most practical problems.
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For a list of universally closed theorems (without schematic term
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variables), monomorphization computes a list of theorems with schematic
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term variables: all polymorphic constants (i.e., constants occurring both
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with ground types and schematic type variables) are instantiated with all
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(necessary) ground types; thereby theorems containing these constants are
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copied. To prevent nontermination, there is an upper limit for the number
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of iterations involved in the fixpoint construction.
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The search for instances is performed on the constants with schematic
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types, which are extracted from the initial set of theorems. The search
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constructs, for each theorem with those constants, a set of substitutions,
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which, in the end, is applied to all corresponding theorems. Remaining
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schematic type variables are substituted with fresh types.
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Searching for necessary substitutions is an iterative fixpoint
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construction: each iteration computes all required instances required by
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the ground instances computed in the previous step and which haven't been
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found before. Computed substitutions are always nontrivial: schematic type
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variables are never mapped to schematic type variables.
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*)
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signature LEGACY_MONOMORPH =
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sig
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(* utility function *)
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val typ_has_tvars: typ -> bool
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val all_schematic_consts_of: term -> typ list Symtab.table
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val add_schematic_consts_of: term -> typ list Symtab.table ->
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typ list Symtab.table
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(* configuration options *)
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val max_rounds: int Config.T
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val max_new_instances: int Config.T
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val keep_partial_instances: bool Config.T
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(* monomorphization *)
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val monomorph: (term -> typ list Symtab.table) -> (int * thm) list ->
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Proof.context -> (int * thm) list list * Proof.context
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end
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structure Legacy_Monomorph: LEGACY_MONOMORPH =
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struct
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(* utility functions *)
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val typ_has_tvars = Term.exists_subtype (fn TVar _ => true | _ => false)
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fun add_schematic_const (c as (_, T)) =
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if typ_has_tvars T then Symtab.insert_list (op =) c else I
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fun add_schematic_consts_of t =
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Term.fold_aterms (fn Const c => add_schematic_const c | _ => I) t
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fun all_schematic_consts_of t = add_schematic_consts_of t Symtab.empty
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(* configuration options *)
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val max_rounds = Attrib.setup_config_int @{binding legacy_monomorph_max_rounds} (K 5)
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val max_new_instances =
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Attrib.setup_config_int @{binding legacy_monomorph_max_new_instances} (K 300)
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val keep_partial_instances =
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Attrib.setup_config_bool @{binding legacy_monomorph_keep_partial_instances} (K true)
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(* monomorphization *)
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(** preparing the problem **)
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datatype thm_info =
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Ground of thm |
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Schematic of {
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index: int,
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theorem: thm,
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tvars: (indexname * sort) list,
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schematics: typ list Symtab.table,
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initial_round: int }
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fun prepare schematic_consts_of rthms =
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let
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val empty_sub = ((0, false, false), Vartab.empty)
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fun prep (r, thm) ((i, idx), (consts, subs)) =
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if not (Term.exists_type typ_has_tvars (Thm.prop_of thm)) then
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(Ground thm, ((i+1, idx + Thm.maxidx_of thm + 1), (consts, subs)))
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else
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let
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(* increase indices to avoid clashes of type variables *)
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val thm' = Thm.incr_indexes idx thm
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val idx' = Thm.maxidx_of thm' + 1
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val schematics = schematic_consts_of (Thm.prop_of thm')
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val consts' =
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Symtab.fold (fn (n, _) => Symtab.update (n, [])) schematics consts
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val subs' = Inttab.update (i, [empty_sub]) subs
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val thm_info = Schematic {
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index = i,
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theorem = thm',
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tvars = Term.add_tvars (Thm.prop_of thm') [],
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schematics = schematics,
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initial_round = r }
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in (thm_info, ((i+1, idx'), (consts', subs'))) end
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in fold_map prep rthms ((0, 0), (Symtab.empty, Inttab.empty)) ||> snd end
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(** collecting substitutions **)
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fun exceeded limit = (limit <= 0)
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fun exceeded_limit (limit, _, _) = exceeded limit
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fun derived_subst subst' subst = subst' |> Vartab.forall (fn (n, (_, T)) =>
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Vartab.lookup subst n |> Option.map (equal T o snd) |> the_default false)
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fun eq_subst (subst1, subst2) =
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derived_subst subst1 subst2 andalso derived_subst subst2 subst1
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fun with_all_grounds cx grounds f =
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if exceeded_limit cx then I else Symtab.fold f grounds
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fun with_all_type_combinations cx schematics f (n, Ts) =
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if exceeded_limit cx then I
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else fold_product f (Symtab.lookup_list schematics n) Ts
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fun derive_new_substs thy cx new_grounds schematics subst =
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with_all_grounds cx new_grounds
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(with_all_type_combinations cx schematics (fn T => fn U =>
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(case try (Sign.typ_match thy (T, U)) subst of
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NONE => I
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| SOME subst' => insert eq_subst subst'))) []
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fun known_subst sub subs1 subs2 subst' =
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let fun derived (_, subst) = derived_subst subst' subst
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in derived sub orelse exists derived subs1 orelse exists derived subs2 end
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fun within_limit f cx = if exceeded_limit cx then cx else f cx
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fun fold_partial_substs derive add = within_limit (
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let
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fun fold_partial [] cx = cx
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| fold_partial (sub :: subs) (limit, subs', next) =
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if exceeded limit then (limit, sub :: subs @ subs', next)
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else sub |> (fn ((generation, full, _), subst) =>
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if full then fold_partial subs (limit, sub :: subs', next)
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else
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(case filter_out (known_subst sub subs subs') (derive subst) of
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[] => fold_partial subs (limit, sub :: subs', next)
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| substs =>
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(limit, ((generation, full, true), subst) :: subs', next)
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|> fold (within_limit o add) substs
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|> fold_partial subs))
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in (fn (limit, subs, next) => fold_partial subs (limit, [], next)) end)
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fun refine ctxt round known_grounds new_grounds (tvars, schematics) cx =
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let
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val thy = Proof_Context.theory_of ctxt
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val count_partial = Config.get ctxt keep_partial_instances
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fun add_new_ground subst n T =
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let val T' = Envir.subst_type subst T
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in
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(* FIXME: maybe keep types in a table or net for known_grounds,
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that might improve efficiency here
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*)
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if typ_has_tvars T' then I
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else if member (op =) (Symtab.lookup_list known_grounds n) T' then I
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else Symtab.cons_list (n, T')
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end
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fun add_new_subst subst (limit, subs, next_grounds) =
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let
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val full = forall (Vartab.defined subst o fst) tvars
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val limit' =
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if full orelse count_partial then limit - 1 else limit
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val sub = ((round, full, false), subst)
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val next_grounds' =
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(schematics, next_grounds)
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|-> Symtab.fold (uncurry (fold o add_new_ground subst))
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in (limit', sub :: subs, next_grounds') end
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in
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fold_partial_substs (derive_new_substs thy cx new_grounds schematics)
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add_new_subst cx
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end
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(*
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'known_grounds' are all constant names known to occur schematically
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associated with all ground instances considered so far
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*)
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fun add_relevant_instances known_grounds (Const (c as (n, T))) =
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if typ_has_tvars T orelse not (Symtab.defined known_grounds n) then I
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else if member (op =) (Symtab.lookup_list known_grounds n) T then I
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else Symtab.insert_list (op =) c
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| add_relevant_instances _ _ = I
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fun collect_instances known_grounds thm =
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Term.fold_aterms (add_relevant_instances known_grounds) (Thm.prop_of thm)
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fun make_subst_ctxt ctxt thm_infos known_grounds substitutions =
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let
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(* The total limit of returned (ground) facts is the number of facts
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given to the monomorphizer increased by max_new_instances. Since
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initially ground facts are returned anyway, the limit here is not
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counting them. *)
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val limit = Config.get ctxt max_new_instances +
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fold (fn Schematic _ => Integer.add 1 | _ => I) thm_infos 0
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fun add_ground_consts (Ground thm) = collect_instances known_grounds thm
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| add_ground_consts (Schematic _) = I
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val initial_grounds = fold add_ground_consts thm_infos Symtab.empty
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in (known_grounds, (limit, substitutions, initial_grounds)) end
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fun is_new round initial_round = (round = initial_round)
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fun is_active round initial_round = (round > initial_round)
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fun fold_schematic pred f = fold (fn
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Schematic {index, theorem, tvars, schematics, initial_round} =>
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if pred initial_round then f theorem (index, tvars, schematics) else I
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| Ground _ => I)
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fun focus f _ (index, tvars, schematics) (limit, subs, next_grounds) =
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let
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val (limit', isubs', next_grounds') =
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(limit, Inttab.lookup_list subs index, next_grounds)
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|> f (tvars, schematics)
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in (limit', Inttab.update (index, isubs') subs, next_grounds') end
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fun collect_substitutions thm_infos ctxt round subst_ctxt =
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let val (known_grounds, (limit, subs, next_grounds)) = subst_ctxt
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in
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if exceeded limit then subst_ctxt
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else
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let
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fun collect thm _ = collect_instances known_grounds thm
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val new = fold_schematic (is_new round) collect thm_infos next_grounds
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val known' = Symtab.merge_list (op =) (known_grounds, new)
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val step = focus o refine ctxt round known'
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in
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(limit, subs, Symtab.empty)
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|> not (Symtab.is_empty new) ?
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fold_schematic (is_active round) (step new) thm_infos
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|> fold_schematic (is_new round) (step known') thm_infos
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|> pair known'
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end
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end
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(** instantiating schematic theorems **)
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fun super_sort (Ground _) S = S
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| super_sort (Schematic {tvars, ...}) S = merge (op =) (S, maps snd tvars)
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fun new_super_type ctxt thm_infos =
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let val S = fold super_sort thm_infos @{sort type}
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in yield_singleton Variable.invent_types S ctxt |>> SOME o TFree end
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fun add_missing_tvar T (ix, S) subst =
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if Vartab.defined subst ix then subst
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else Vartab.update (ix, (S, T)) subst
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fun complete tvars subst T =
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subst
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|> Vartab.map (K (apsnd (Term.map_atyps (fn TVar _ => T | U => U))))
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|> fold (add_missing_tvar T) tvars
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fun instantiate_all' (mT, ctxt) subs thm_infos =
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let
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val thy = Proof_Context.theory_of ctxt
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fun cert (ix, (S, T)) = pairself (Thm.ctyp_of thy) (TVar (ix, S), T)
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fun cert' subst = Vartab.fold (cons o cert) subst []
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fun instantiate thm subst = Thm.instantiate (cert' subst, []) thm
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fun with_subst tvars f ((generation, full, _), subst) =
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if full then SOME (generation, f subst)
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else Option.map (pair generation o f o complete tvars subst) mT
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fun inst (Ground thm) = [(0, thm)]
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| inst (Schematic {theorem, tvars, index, ...}) =
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Inttab.lookup_list subs index
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|> map_filter (with_subst tvars (instantiate theorem))
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in (map inst thm_infos, ctxt) end
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fun instantiate_all ctxt thm_infos (_, (_, subs, _)) =
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if Config.get ctxt keep_partial_instances then
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let fun is_refined ((_, _, refined), _) = refined
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in
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(Inttab.map (K (filter_out is_refined)) subs, thm_infos)
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|-> instantiate_all' (new_super_type ctxt thm_infos)
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end
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else instantiate_all' (NONE, ctxt) subs thm_infos
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(** overall procedure **)
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fun limit_rounds ctxt f =
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let
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val max = Config.get ctxt max_rounds
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fun round i x = if i > max then x else round (i + 1) (f ctxt i x)
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in round 1 end
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fun monomorph schematic_consts_of rthms ctxt =
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let
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val (thm_infos, (known_grounds, subs)) = prepare schematic_consts_of rthms
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in
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if Symtab.is_empty known_grounds then
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(map (fn Ground thm => [(0, thm)] | _ => []) thm_infos, ctxt)
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else
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make_subst_ctxt ctxt thm_infos known_grounds subs
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|> limit_rounds ctxt (collect_substitutions thm_infos)
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|> instantiate_all ctxt thm_infos
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end
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end
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