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cc0195fef5
polymorphism.nl: Make sure that if we introduce any extra head variables, we fix up the quantification information in the goal_info.
477 lines
18 KiB
Mathematica
477 lines
18 KiB
Mathematica
%-----------------------------------------------------------------------------%
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%-----------------------------------------------------------------------------%
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% file: polymorphism.nl
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% main author: fjh
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% This module is a pass over the HLDS.
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% It does a syntactic transformation to implement polymorphic unifications
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% using higher-order predicates. Every polymorphic predicate is transformed
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% so that it takes one additional argument for every type variable in the
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% predicate's type declaration. The argument is a higher-order predicate
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% argument which is (the address of) the unification predicate for that type.
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% Every polymorphic unification is replaced by a call to one of these
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% predicates.
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%
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% For example, we translate
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%
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% :- pred p(T1).
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% :- pred q(T2).
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% :- pred r(T3).
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% p(X) :- q([X]), r(0).
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%
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% into
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%
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% :- pred p(T1, pred(T1, T1)).
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% :- pred q(T2, pred(T2, T2)).
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% :- pred r(T3, pred(T2, T2)).
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% p(X, Unify) :- q([X], list_unify(Unify)), r(0, int_unify).
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%
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% (except that both the input and output of the transformation are
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% actually in super-homogeneous form).
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%-----------------------------------------------------------------------------%
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:- module polymorphism.
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:- interface.
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:- import_module hlds.
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:- pred polymorphism__process_module(module_info, module_info).
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:- mode polymorphism__process_module(in, out) is det.
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%-----------------------------------------------------------------------------%
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%-----------------------------------------------------------------------------%
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:- implementation.
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:- import_module int, list, set, map, term, varset, std_util, require.
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:- import_module prog_io, type_util, mode_util, quantification.
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%-----------------------------------------------------------------------------%
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% This whole section just traverses the module structure.
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% We do two passes, the first to fix up the procedure bodies,
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% (and in fact everything except the pred_info argtypes),
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% the second to fix up the pred_info argtypes.
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% The reason we need two passes is that the first pass looks at
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% the argtypes of the called predicates, and so we need to make
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% sure we don't much them up before we've finished the first pass.
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polymorphism__process_module(ModuleInfo0, ModuleInfo) :-
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module_info_preds(ModuleInfo0, Preds),
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map__keys(Preds, PredIds),
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polymorphism__process_preds(PredIds, ModuleInfo0, ModuleInfo1),
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polymorphism__fixup_preds(PredIds, ModuleInfo1, ModuleInfo).
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:- pred polymorphism__process_preds(list(pred_id), module_info, module_info).
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:- mode polymorphism__process_preds(in, in, out) is det.
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polymorphism__process_preds([], ModuleInfo, ModuleInfo).
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polymorphism__process_preds([PredId | PredIds], ModuleInfo0, ModuleInfo) :-
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module_info_pred_info(ModuleInfo0, PredId, PredInfo),
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pred_info_procids(PredInfo, ProcIds),
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polymorphism__process_procs(PredId, ProcIds, ModuleInfo0, ModuleInfo1),
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polymorphism__process_preds(PredIds, ModuleInfo1, ModuleInfo).
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:- pred polymorphism__process_procs(pred_id, list(proc_id),
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module_info, module_info).
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:- mode polymorphism__process_procs(in, in, in, out) is det.
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polymorphism__process_procs(_PredId, [], ModuleInfo, ModuleInfo).
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polymorphism__process_procs(PredId, [ProcId | ProcIds], ModuleInfo0,
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ModuleInfo) :-
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module_info_preds(ModuleInfo0, PredTable0),
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map__lookup(PredTable0, PredId, PredInfo0),
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pred_info_procedures(PredInfo0, ProcTable0),
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map__lookup(ProcTable0, ProcId, ProcInfo0),
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polymorphism__process_proc(ProcInfo0, PredInfo0, ModuleInfo0,
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ProcInfo, PredInfo1),
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map__set(ProcTable0, ProcId, ProcInfo, ProcTable),
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pred_info_set_procedures(PredInfo1, ProcTable, PredInfo),
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map__set(PredTable0, PredId, PredInfo, PredTable),
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module_info_set_preds(ModuleInfo0, PredTable, ModuleInfo1),
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polymorphism__process_procs(PredId, ProcIds, ModuleInfo1, ModuleInfo).
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%---------------------------------------------------------------------------%
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:- pred polymorphism__fixup_preds(list(pred_id), module_info, module_info).
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:- mode polymorphism__fixup_preds(in, in, out) is det.
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polymorphism__fixup_preds([], ModuleInfo, ModuleInfo).
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polymorphism__fixup_preds([PredId | PredIds], ModuleInfo0, ModuleInfo) :-
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%
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% recompute the arg types by finding the headvars and the var->type
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% mapping (from the first procedure for the predicate) and
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% applying the type mapping to the headvars to get the new arg types
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%
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module_info_preds(ModuleInfo0, PredTable0),
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map__lookup(PredTable0, PredId, PredInfo0),
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pred_info_procedures(PredInfo0, ProcTable0),
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pred_info_proc_ids(PredInfo0, ProcIds),
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( ProcIds = [ProcId|_] ->
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map__lookup(ProcTable0, ProcId, ProcInfo)
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;
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error("polymorphism__fixup_preds: empty procid list")
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),
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proc_info_vartypes(ProcInfo, VarTypes),
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proc_info_headvars(ProcInfo, HeadVars),
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map__apply_to_list(HeadVars, VarTypes, ArgTypes),
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pred_info_arg_types(PredInfo0, TypeVarSet, _ArgTypes0),
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pred_info_set_arg_types(PredInfo0, TypeVarSet, ArgTypes, PredInfo),
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map__set(PredTable0, PredId, PredInfo, PredTable),
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module_info_set_preds(ModuleInfo0, PredTable, ModuleInfo1),
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polymorphism__fixup_preds(PredIds, ModuleInfo1, ModuleInfo).
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%---------------------------------------------------------------------------%
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:- type poly_info --->
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poly_info(
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varset, % from the proc_info
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map(var, type), % from the proc_info
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tvarset, % from the proc_info
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map(tvar, var), % specifies the unify proc var
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% for each of the pred's type
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% parameters
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module_info
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).
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:- pred polymorphism__process_proc(proc_info, pred_info, module_info,
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proc_info, pred_info).
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:- mode polymorphism__process_proc(in, in, in, out, out) is det.
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polymorphism__process_proc(ProcInfo0, PredInfo0, ModuleInfo,
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ProcInfo, PredInfo) :-
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% grab the appropriate fields from the pred_info and proc_info
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pred_info_arg_types(PredInfo0, TypeVarSet0, ArgTypes0),
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proc_info_headvars(ProcInfo0, HeadVars0),
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proc_info_variables(ProcInfo0, VarSet0),
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proc_info_vartypes(ProcInfo0, VarTypes0),
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proc_info_goal(ProcInfo0, Goal0),
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proc_info_argmodes(ProcInfo0, ArgModes0),
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% insert extra head variables to hold the address of the
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% equality predicate for each polymorphic type in the predicate's
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% type declaration
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term__vars_list(ArgTypes0, HeadTypeVars0),
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list__sort(HeadTypeVars0, HeadTypeVars), % remove duplicates
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polymorphism__make_head_vars(HeadTypeVars, VarSet0, VarTypes0,
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ExtraHeadVars, VarSet1, VarTypes1),
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list__append(HeadVars0, ExtraHeadVars, HeadVars),
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%
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% We don't update the argtypes here, it's done in the next pass
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% map__apply_to_list(ExtraHeadVars, VarTypes1, ExtraArgTypes),
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% list__append(ArgTypes0, ExtraArgTypes, ArgTypes),
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%
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list__length(ExtraHeadVars, NumExtraVars),
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list__duplicate(NumExtraVars, ground -> ground, ExtraModes),
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list__append(ArgModes0, ExtraModes, ArgModes),
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( pred_info_is_imported(PredInfo0) ->
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VarTypes = VarTypes1,
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VarSet = VarSet1,
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TypeVarSet = TypeVarSet0,
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Goal = Goal0
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;
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% process any polymorphic calls inside the goal
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map__from_corresponding_lists(HeadTypeVars, ExtraHeadVars,
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UnifyProcMap),
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Info0 = poly_info(VarSet1, VarTypes1, TypeVarSet0,
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UnifyProcMap, ModuleInfo),
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polymorphism__process_goal(Goal0, Goal1, Info0, Info),
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Info = poly_info(VarSet, VarTypes, TypeVarSet, _, _),
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% if we introduced any new head variables, we need to
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% fix up the quantification (non-local variables)
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( ExtraHeadVars = [] ->
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Goal = Goal1
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;
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implicitly_quantify_clause_body(HeadVars, Goal1, Goal)
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)
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),
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% set the new values of the fields in proc_info and pred_info
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proc_info_set_headvars(ProcInfo0, HeadVars, ProcInfo1),
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proc_info_set_goal(ProcInfo1, Goal, ProcInfo2),
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proc_info_set_varset(ProcInfo2, VarSet, ProcInfo3),
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proc_info_set_vartypes(ProcInfo3, VarTypes, ProcInfo4),
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proc_info_set_argmodes(ProcInfo4, ArgModes, ProcInfo),
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pred_info_set_arg_types(PredInfo0, TypeVarSet, ArgTypes0, PredInfo).
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:- pred polymorphism__process_goal(hlds__goal, hlds__goal,
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poly_info, poly_info).
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:- mode polymorphism__process_goal(in, out, in, out) is det.
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polymorphism__process_goal(Goal0 - GoalInfo0, Goal) -->
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polymorphism__process_goal_2(Goal0, GoalInfo0, Goal).
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:- pred polymorphism__process_goal_2(hlds__goal_expr, hlds__goal_info,
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hlds__goal, poly_info, poly_info).
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:- mode polymorphism__process_goal_2(in, in, out, in, out) is det.
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polymorphism__process_goal_2(
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call(PredId, ProcId, Args0, Builtin, Name, FollowVars),
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GoalInfo, Goal) -->
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{ term__term_list_to_var_list(Args0, ArgVars0) },
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polymorphism__process_call(PredId, ProcId, ArgVars0,
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ArgVars, ExtraGoals),
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{ term__var_list_to_term_list(ArgVars, Args) },
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{ Call = call(PredId, ProcId, Args, Builtin, Name, FollowVars)
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- GoalInfo },
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{ list__append(ExtraGoals, [Call], GoalList) },
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{ conj_list_to_goal(GoalList, GoalInfo, Goal) }.
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% XXX handle polymorphic unifications!
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polymorphism__process_goal_2(unify(X, Y, Unification, Mode, Context), GoalInfo,
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unify(X, Y, Unification, Mode, Context) - GoalInfo) --> [].
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% the rest of the clauses just process goals recursively
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polymorphism__process_goal_2(conj(Goals0), GoalInfo, conj(Goals) - GoalInfo) -->
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polymorphism__process_goal_list(Goals0, Goals).
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polymorphism__process_goal_2(disj(Goals0), GoalInfo, disj(Goals) - GoalInfo) -->
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polymorphism__process_goal_list(Goals0, Goals).
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polymorphism__process_goal_2(not(Goal0), GoalInfo, not(Goal) - GoalInfo) -->
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polymorphism__process_goal(Goal0, Goal).
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polymorphism__process_goal_2(switch(_, _, _), _, _) -->
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{ error("polymorphism__process_goal_2: switch unexpected") }.
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polymorphism__process_goal_2(some(Vars, Goal0), GoalInfo,
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some(Vars, Goal) - GoalInfo) -->
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polymorphism__process_goal(Goal0, Goal).
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polymorphism__process_goal_2(if_then_else(Vars, A0, B0, C0), GoalInfo,
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if_then_else(Vars, A, B, C) - GoalInfo) -->
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polymorphism__process_goal(A0, A),
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polymorphism__process_goal(B0, B),
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polymorphism__process_goal(C0, C).
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:- pred polymorphism__process_goal_list(list(hlds__goal), list(hlds__goal),
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poly_info, poly_info).
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:- mode polymorphism__process_goal_list(in, out, in, out) is det.
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polymorphism__process_goal_list([], []) --> [].
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polymorphism__process_goal_list([Goal0 | Goals0], [Goal | Goals]) -->
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polymorphism__process_goal(Goal0, Goal),
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polymorphism__process_goal_list(Goals0, Goals).
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:- pred polymorphism__process_call(pred_id, proc_id, list(var),
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list(var), list(hlds__goal),
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poly_info, poly_info).
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:- mode polymorphism__process_call(in, in, in, out, out, in, out) is det.
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polymorphism__process_call(PredId, _ProcId, ArgVars0, ArgVars, ExtraGoals,
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Info0, Info) :-
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Info0 = poly_info(VarSet0, VarTypes0, TypeVarSet0,
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UnifyProcMap, ModuleInfo),
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module_info_pred_info(ModuleInfo, PredId, PredInfo),
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pred_info_arg_types(PredInfo, PredTypeVarSet, PredArgTypes0),
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% rename apart
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% XXX this merge may be a performance bottleneck:
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% it gets executed O(m) times,
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% each merge takes O(size of PredTypeVarSet) = O(n) insertions,
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% each insertion takes O(log(n)) for the search plus
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% (in the worst case, if all the types are named "T")
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% O(n*n) for the variable naming.
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% So overall it's O(m * n^3).
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% (m = number of predicates, n = predicate size)
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varset__merge(TypeVarSet0, PredTypeVarSet, PredArgTypes0,
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TypeVarSet, PredArgTypes),
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term__vars_list(PredArgTypes, PredTypeVars0),
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( PredTypeVars0 = [] ->
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% optimize for common case of non-polymorphic call
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ArgVars = ArgVars0,
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ExtraGoals = [],
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Info = Info0
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;
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list__sort(PredTypeVars0, PredTypeVars), % eliminate duplicates
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map__apply_to_list(ArgVars0, VarTypes0, ActualArgTypes),
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map__keys(UnifyProcMap, HeadTypeVars),
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map__init(TypeSubst0),
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( type_unify_list(ActualArgTypes, PredArgTypes, HeadTypeVars,
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TypeSubst0, TypeSubst1) ->
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TypeSubst = TypeSubst1
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;
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error("polymorphism__process_goal_2: type unification failed")
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),
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term__var_list_to_term_list(PredTypeVars, PredTypes0),
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term__apply_rec_substitution_to_list(PredTypes0, TypeSubst,
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PredTypes),
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polymorphism__make_vars(PredTypes, UnifyProcMap, VarSet0,
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VarTypes0, ExtraVars, ExtraGoals, VarSet, VarTypes),
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list__append(ArgVars0, ExtraVars, ArgVars),
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Info = poly_info(VarSet, VarTypes, TypeVarSet,
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UnifyProcMap, ModuleInfo)
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).
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%---------------------------------------------------------------------------%
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:- pred polymorphism__make_vars(list(type), map(tvar, var),
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varset, map(var, type),
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list(var), list(hlds__goal),
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varset, map(var, type)).
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:- mode polymorphism__make_vars(in, in, in, in, out, out, out, out) is det.
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polymorphism__make_vars([], _, VarSet, VarTypes, [], [], VarSet, VarTypes).
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polymorphism__make_vars([Type|Types], UnifyProcMap, VarSet0, VarTypes0,
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ExtraVars, ExtraGoals, VarSet, VarTypes) :-
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(
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Type = term__functor(_TypeName, TypeArgs, Context)
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->
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% This occurs for code where a predicate calls a polymorphic
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% predicate with a known value of the type variable.
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% For example, given
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%
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% :- pred p(T1).
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% :- pred q(T2).
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% :- pred r(T3).
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% p(X) :- q([X]), r(0).
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%
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% we know that in the call to q/1, T2 is bound to `list(T1)',
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% and in the call to r/1, T3 is bound to `int', and so
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% we translate it into
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% :- pred p(T1, pred(T1, T1)).
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% :- pred q(T2, pred(T2, T2)).
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% :- pred r(T3, pred(T3, T3)).
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% p(X, Unify) :- q([X], list_unify(Unify)), r(int_unify).
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% create a term which holds the unification pred for
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% the type, processing any argument types recursively
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polymorphism__make_vars(TypeArgs, UnifyProcMap,
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VarSet0, VarTypes0,
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ArgVars, ExtraGoals0, VarSet1, VarTypes1),
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term__var_list_to_term_list(ArgVars, Args),
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Functor = term__atom("="),
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ValTerm = term__functor(Functor, Args, Context),
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ConsId = cons("=", 2),
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% introduce new variable
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varset__new_var(VarSet1, Var, VarSet2),
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UnifyPredType = term__functor(term__atom("pred"),
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[Type, Type],
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Context),
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map__set(VarTypes1, Var, UnifyPredType, VarTypes2),
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VarTerm = term__variable(Var),
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% create a construction unification which initializes the
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% variable to the unification pred for the type
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UniMode = (free - ground -> ground - ground),
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list__length(ArgVars, NumArgVars),
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list__duplicate(NumArgVars, UniMode, UniModes),
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Unification = construct(Var, ConsId, ArgVars, UniModes),
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UnifyMode = (free -> ground) - (ground -> ground),
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UnifyContext = unify_context(explicit, []),
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% XXX the UnifyContext is wrong
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Unify = unify(VarTerm, ValTerm, UnifyMode, Unification,
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UnifyContext),
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% create a goal_info for the unification
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goal_info_init(GoalInfo0),
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set__list_to_set([Var | ArgVars], NonLocals),
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goal_info_set_nonlocals(GoalInfo0, NonLocals, GoalInfo1),
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map__init(InstMapping0),
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list__duplicate(NumArgVars, ground, ArgInsts),
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% note that we could perhaps be more accurate than
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% `ground', but hopefully it shouldn't make any
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% difference.
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map__set(InstMapping0, Var, bound([functor(Functor, ArgInsts)]),
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InstMapping),
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goal_info_set_instmap_delta(GoalInfo1, reachable(InstMapping),
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GoalInfo),
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ExtraGoal = Unify - GoalInfo,
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list__append(ExtraGoals0, [ExtraGoal], ExtraGoals1)
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;
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Type = term__variable(TypeVar1),
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map__search(UnifyProcMap, TypeVar1, UnifyProcVar)
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->
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% This occurs for code where a predicate calls a polymorphic
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% predicate with a bound but unknown value of the type variable.
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% For example, in
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%
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% :- pred p(T1).
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% :- pred q(T2).
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% p(X) :- q(X).
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%
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% we know that `T2' is bound to `T1', and we translate it into
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%
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% :- pred p(T1, pred(T1, T1)).
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% :- pred q(T2, pred(T2, T2)).
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% p(X, UnifyProc) :- q(X, UnifyProc).
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Var = UnifyProcVar,
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ExtraGoals1 = [],
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VarSet2 = VarSet0,
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VarTypes2 = VarTypes0
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;
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% This occurs for code where a predicate calls a polymorphic
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% predicate with an unbound type variable, for example
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%
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% :- pred p.
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% :- pred q(list(T)).
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% p :- q([]).
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%
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% In this case T is unbound, so there cannot be any objects
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% ot type T, and so q/1 cannot possibly use the unification
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% predicate for type T. We just pass a dummy value (zero).
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%
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% :- pred p.
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% :- pred q(T, pred(T, T)).
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% p :- q([], 0).
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%
|
|
% (This isn't really type-correct, but we're already past
|
|
% the type-checker. Passing 0 should ensure that we get
|
|
% a core dump if we ever attempt to call the unify pred.)
|
|
|
|
% introduce new variable
|
|
varset__new_var(VarSet0, Var, VarSet2),
|
|
UnifyPredType = term__functor(term__atom("pred"),
|
|
[Type, Type],
|
|
Context),
|
|
map__set(VarTypes0, Var, UnifyPredType, VarTypes2),
|
|
VarTerm = term__variable(Var),
|
|
|
|
% create a construction unification which initializes the
|
|
% variable to zero
|
|
term__context_init(0, Context),
|
|
Functor = term__integer(0),
|
|
ZeroTerm = term__functor(Functor, [], Context),
|
|
ConsId = int_const(0),
|
|
Unification = construct(Var, ConsId, [], []),
|
|
UnifyMode = (free -> ground) - (ground -> ground),
|
|
UnifyContext = unify_context(explicit, []),
|
|
% XXX the UnifyContext is wrong
|
|
Unify = unify(VarTerm, ZeroTerm, UnifyMode, Unification,
|
|
UnifyContext),
|
|
goal_info_init(GoalInfo0),
|
|
set__singleton_set(NonLocals, Var),
|
|
goal_info_set_nonlocals(GoalInfo0, NonLocals, GoalInfo1),
|
|
map__init(InstMapping0),
|
|
map__set(InstMapping0, Var, bound([functor(Functor, [])]),
|
|
InstMapping),
|
|
goal_info_set_instmap_delta(GoalInfo1, reachable(InstMapping),
|
|
GoalInfo),
|
|
Goal = Unify - GoalInfo,
|
|
ExtraGoals1 = [Goal]
|
|
),
|
|
ExtraVars = [Var | ExtraVars1],
|
|
list__append(ExtraGoals1, ExtraGoals2, ExtraGoals),
|
|
polymorphism__make_vars(Types, UnifyProcMap, VarSet2, VarTypes2,
|
|
ExtraVars1, ExtraGoals2, VarSet, VarTypes).
|
|
|
|
:- pred polymorphism__make_head_vars(list(tvar), varset, map(var, type),
|
|
list(var), varset, map(var, type)).
|
|
:- mode polymorphism__make_head_vars(in, in, in, out, out, out) is det.
|
|
|
|
polymorphism__make_head_vars([], VarSet, VarTypes, [], VarSet, VarTypes).
|
|
polymorphism__make_head_vars([TypeVar|TypeVars], VarSet0, VarTypes0,
|
|
UnifyProcVars, VarSet, VarTypes) :-
|
|
varset__new_var(VarSet0, Var, VarSet1),
|
|
term__context_init(0, Context),
|
|
Type = term__variable(TypeVar),
|
|
UnifyPredType = term__functor(term__atom("pred"), [Type, Type],
|
|
Context),
|
|
map__set(VarTypes0, Var, UnifyPredType, VarTypes1),
|
|
UnifyProcVars = [Var | UnifyProcVars1],
|
|
polymorphism__make_head_vars(TypeVars, VarSet1, VarTypes1,
|
|
UnifyProcVars1, VarSet, VarTypes).
|
|
|
|
%---------------------------------------------------------------------------%
|
|
%---------------------------------------------------------------------------%
|