trans.icl

/*
	module owner: Diederik van Arkel
*/
implementation module trans

import StdEnv

import syntax, transform, checksupport, StdCompare, check, utilities, unitype, typesupport, type
import classify, partition

SwitchCaseFusion			fuse dont_fuse :== fuse
SwitchGeneratedFusion		fuse dont_fuse :== fuse
SwitchFunctionFusion		fuse dont_fuse :== fuse
SwitchConstructorFusion		fuse dont_fuse :== dont_fuse
SwitchRnfConstructorFusion  rnf  linear	   :== rnf
SwitchCurriedFusion			fuse xtra dont_fuse :== fuse 
SwitchExtraCurriedFusion	fuse macro :== (fuse && macro)//fuse
SwitchTrivialFusion			fuse dont_fuse :== fuse
SwitchUnusedFusion			fuse dont_fuse :== fuse
SwitchReanalyseFunction		rean dont_rean :== dont_rean
SwitchTransformConstants	tran dont_tran :== tran
SwitchSpecialFusion			fuse dont_fuse :== fuse
SwitchArityChecks			check dont_check :== check
SwitchNWayFusion			fuse dont_fuse :== dont_fuse
SwitchDirectConsumerUnfold	unfold dont    :== dont
SwitchAutoFoldCaseInCase	fold dont	   :== fold
SwitchAutoFoldAppInCase		fold dont	   :== fold
SwitchAlwaysIntroduceCaseFunction yes no   :== no//yes
SwitchNonRecFusion			fuse dont_fuse :== dont_fuse
SwitchHOFusion				fuse dont_fuse :== fuse
SwitchHOFusion`				fuse dont_fuse :== fuse

//import RWSDebug

(-!->) infix
(-!->) a b :== a  // ---> b
(<-!-) infix
(<-!-) a b :== a  // <--- b

fromYes (Yes x) = x

is_SK_Function_or_SK_LocalMacroFunction (SK_Function _) = True
is_SK_Function_or_SK_LocalMacroFunction (SK_LocalMacroFunction _) = True
is_SK_Function_or_SK_LocalMacroFunction _ = False

undeff :== -1

empty_atype = { at_attribute = TA_Multi, at_type = TE }

get_producer_symbol (PR_Curried symbol arity)
	= (symbol,arity)
get_producer_symbol (PR_Function symbol arity _)
	= (symbol,arity)
get_producer_symbol (PR_GeneratedFunction symbol arity _)
	= (symbol,arity)
get_producer_symbol (PR_Constructor symbol arity _)
	= (symbol,arity)

// Extended variable info accessors...

readVarInfo :: VarInfoPtr *VarHeap -> (VarInfo, !*VarHeap)
readVarInfo var_info_ptr var_heap
	# (var_info, var_heap) = readPtr var_info_ptr var_heap
	= case var_info of
		VI_Extended _ original_var_info	-> (original_var_info, var_heap)
		_								-> (var_info, var_heap)

readExtendedVarInfo :: VarInfoPtr *VarHeap -> (ExtendedVarInfo, !*VarHeap)
readExtendedVarInfo var_info_ptr var_heap
	# (var_info, var_heap) = readPtr var_info_ptr var_heap
	= case var_info of
		VI_Extended extensions _	-> (extensions, var_heap)
		_							-> abort "sanity check 'readExtendedVarInfo' failed in module trans.\n"

writeVarInfo :: VarInfoPtr VarInfo *VarHeap -> *VarHeap
writeVarInfo var_info_ptr new_var_info var_heap
	# (old_var_info, var_heap) = readPtr var_info_ptr var_heap
	= case old_var_info of
		VI_Extended extensions _	-> writePtr var_info_ptr (VI_Extended extensions new_var_info) var_heap
		_							-> writePtr var_info_ptr new_var_info var_heap

setExtendedVarInfo :: !VarInfoPtr !ExtendedVarInfo !*VarHeap -> *VarHeap
setExtendedVarInfo var_info_ptr extension var_heap
	# (old_var_info, var_heap) = readPtr var_info_ptr var_heap
	= case old_var_info of
		VI_Extended _ original_var_info	-> writePtr var_info_ptr (VI_Extended extension original_var_info) var_heap
		_								-> writePtr var_info_ptr (VI_Extended extension old_var_info) var_heap

// Extended expression info accessors...

readExprInfo :: !ExprInfoPtr !*ExpressionHeap -> (!ExprInfo,!*ExpressionHeap)
readExprInfo expr_info_ptr symbol_heap
	# (expr_info, symbol_heap) = readPtr expr_info_ptr symbol_heap
	= case expr_info of
		EI_Extended _ ei	-> (ei, symbol_heap)
		_					-> (expr_info, symbol_heap)

writeExprInfo :: !ExprInfoPtr !ExprInfo !*ExpressionHeap -> *ExpressionHeap
writeExprInfo expr_info_ptr new_expr_info symbol_heap
	# (expr_info, symbol_heap) = readPtr expr_info_ptr symbol_heap
	= case expr_info of
		EI_Extended extensions _	-> writePtr expr_info_ptr (EI_Extended extensions new_expr_info) symbol_heap
		_							-> writePtr expr_info_ptr new_expr_info symbol_heap

app_EEI_ActiveCase transformer expr_info_ptr expr_heap
	# (expr_info, expr_heap) = readPtr expr_info_ptr expr_heap
	= case expr_info of
		(EI_Extended (EEI_ActiveCase aci) original_expr_info)
			-> writePtr expr_info_ptr (EI_Extended (EEI_ActiveCase (transformer aci)) original_expr_info) expr_heap
		_	-> expr_heap

set_aci_free_vars_info_case unbound_variables case_info_ptr expr_heap
	= app_EEI_ActiveCase (\aci -> { aci & aci_free_vars=Yes unbound_variables }) case_info_ptr expr_heap

remove_aci_free_vars_info case_info_ptr expr_heap
	= app_EEI_ActiveCase (\aci->{aci & aci_free_vars = No }) case_info_ptr expr_heap

cleanup_attributes expr_info_ptr symbol_heap
	# (expr_info, symbol_heap) = readPtr expr_info_ptr symbol_heap
	= case expr_info of
		EI_Extended _ expr_info -> writePtr expr_info_ptr expr_info symbol_heap
		_ -> symbol_heap

/*
 *	TRANSFORM
 */

::	*TransformInfo =
	{	ti_fun_defs				:: !*{# FunDef}
	,	ti_instances 			:: !*{! InstanceInfo }
	,	ti_cons_args 			:: !*{! ConsClasses}
	,	ti_new_functions 		:: ![FunctionInfoPtr]
	,	ti_fun_heap				:: !*FunctionHeap
	,	ti_var_heap				:: !*VarHeap
	,	ti_symbol_heap			:: !*ExpressionHeap
	,	ti_type_heaps			:: !*TypeHeaps
	,	ti_type_def_infos		:: !*TypeDefInfos
	,	ti_next_fun_nr			:: !Index
	,	ti_cleanup_info			:: !CleanupInfo
	,	ti_recursion_introduced	:: !Optional Index
//	,	ti_trace				:: !Bool // XXX just for tracing
	,	ti_error_file			:: !*File
	,	ti_predef_symbols		:: !*PredefinedSymbols
	}

::	ReadOnlyTI = 
	{	ro_imported_funs	:: !{# {# FunType} }
	,	ro_common_defs		:: !{# CommonDefs }
// the following four are used when possibly generating functions for cases...
	,	ro_root_case_mode		:: !RootCaseMode
	,	ro_fun_root				:: !SymbIdent		// original function
	,	ro_fun_case				:: !SymbIdent		// original function or possibly generated case
	,	ro_fun_args				:: ![FreeVar]		// args of above
	,	ro_fun_geni				:: !(!Int,!Int)
	,	ro_fun_orig				:: !SymbIdent		// original consumer

	,	ro_main_dcl_module_n 	:: !Int

	,	ro_transform_fusion		:: !Bool			// fusion switch

	,	ro_stdStrictLists_module_n :: !Int
	}

::	RootCaseMode = NotRootCase | RootCase | RootCaseOfZombie

neverMatchingCase (Yes ident)
	# ident = ident -!-> ("neverMatchingCase",ident)
	= FailExpr ident
neverMatchingCase _ 
	# ident = {id_name = "neverMatchingCase", id_info = nilPtr}  -!-> "neverMatchingCase without ident\n"
	= FailExpr ident
/*
	= Case { case_expr = EE, case_guards = NoPattern, case_default = No, case_ident = ident, case_info_ptr = nilPtr, 
// RWS ...
						case_explicit = False,
				//		case_explicit = True,	// DvA better?
// ... RWS
						case_default_pos = NoPos }
*/
class transform a :: !a !ReadOnlyTI !*TransformInfo -> (!a, !*TransformInfo)

instance transform Expression
where
	transform expr=:(App app=:{app_symb,app_args}) ro ti
		# (app_args, ti) = transform app_args ro ti
		= transformApplication { app & app_args = app_args } [] ro ti
	transform appl_expr=:(expr @ exprs) ro ti
		# (expr, ti) = transform expr ro ti
		  (exprs, ti) = transform exprs ro ti
		= case expr of
			App app
				-> transformApplication app exprs ro ti
			_
				-> (expr @ exprs, ti)
	transform (Let lad=:{let_strict_binds, let_lazy_binds, let_expr}) ro ti
		# ti = store_type_info_of_bindings_in_heap lad ti
		  (let_strict_binds, ti) = transform let_strict_binds ro ti
		  (let_lazy_binds, ti) = transform let_lazy_binds ro ti
		  (let_expr, ti) = transform let_expr ro ti
		  lad = { lad & let_lazy_binds = let_lazy_binds, let_strict_binds = let_strict_binds, let_expr = let_expr}
//		  ti = check_type_info lad ti
		= (Let lad, ti)
	  where
		store_type_info_of_bindings_in_heap {let_strict_binds, let_lazy_binds,let_info_ptr} ti
			# let_binds = let_strict_binds ++ let_lazy_binds
			# (EI_LetType var_types, ti_symbol_heap) = readExprInfo let_info_ptr ti.ti_symbol_heap
			  ti_var_heap								= foldSt store_type_info_let_bind
								   (zip2 var_types let_binds) ti.ti_var_heap
								   //  ---> ("store_type_info_of_bindings_in_heap",let_strict_binds,let_lazy_binds,var_types)
			= { ti & ti_symbol_heap = ti_symbol_heap, ti_var_heap = ti_var_heap }
		store_type_info_let_bind (var_type, {lb_dst={fv_info_ptr}}) var_heap
			= setExtendedVarInfo fv_info_ptr (EVI_VarType var_type) var_heap
		check_type_info {let_strict_binds,let_lazy_binds,let_info_ptr} ti
			# (EI_LetType var_types, ti_symbol_heap) = readExprInfo let_info_ptr ti.ti_symbol_heap
			= { ti & ti_symbol_heap = ti_symbol_heap }
				//  ---> ("check_type_info_of_bindings_in_heap",let_strict_binds,let_lazy_binds,var_types)

	transform (Case kees) ro ti
		# ti = store_type_info_of_patterns_in_heap kees ti
		= transformCase kees ro ti
	  where
		store_type_info_of_patterns_in_heap {case_guards,case_info_ptr} ti
			= case case_guards of
				AlgebraicPatterns _ patterns
					# (EI_CaseType {ct_cons_types},ti_symbol_heap)
										= readExprInfo case_info_ptr ti.ti_symbol_heap
					  ti_var_heap = foldSt store_type_info_of_alg_pattern (zip2 ct_cons_types patterns) ti.ti_var_heap
					-> { ti & ti_symbol_heap = ti_symbol_heap, ti_var_heap = ti_var_heap }
				BasicPatterns _ _
					-> ti // no variables occur
				OverloadedListPatterns _ _ patterns
					# (EI_CaseType {ct_cons_types},ti_symbol_heap)
										= readExprInfo case_info_ptr ti.ti_symbol_heap
					  ti_var_heap = foldSt store_type_info_of_alg_pattern (zip2 ct_cons_types patterns) ti.ti_var_heap
					-> { ti & ti_symbol_heap = ti_symbol_heap, ti_var_heap = ti_var_heap }
				NoPattern
					-> ti
		store_type_info_of_alg_pattern (var_types,{ap_vars}) var_heap
			= foldSt store_type_info_of_pattern_var (zip2 var_types ap_vars) var_heap
		store_type_info_of_pattern_var (var_type, {fv_info_ptr}) var_heap
			= setExtendedVarInfo fv_info_ptr (EVI_VarType var_type) var_heap

	transform (Selection opt_type expr selectors) ro ti
		# (expr, ti) = transform expr ro ti
		= transformSelection opt_type selectors expr ro ti
	transform (Update expr1 selectors expr2) ro ti
		# (expr1,ti) = transform expr1 ro ti
		# (selectors,ti) = transform_expressions_in_selectors selectors ti
			with
				transform_expressions_in_selectors [selection=:RecordSelection _ _ : selections] ti
					# (selections,ti) = transform_expressions_in_selectors selections ti
					= ([selection:selections],ti)
				transform_expressions_in_selectors [ArraySelection ds ep expr : selections] ti
					# (expr,ti) = transform expr ro ti
					# (selections,ti) = transform_expressions_in_selectors selections ti
					= ([ArraySelection ds ep expr:selections],ti)
				transform_expressions_in_selectors [DictionarySelection bv dictionary_selections ep expr : selections] ti
					# (expr,ti) = transform expr ro ti
					# (dictionary_selections,ti) = transform_expressions_in_selectors dictionary_selections ti
					# (selections,ti) = transform_expressions_in_selectors selections ti
					= ([DictionarySelection bv dictionary_selections ep expr:selections],ti)
				transform_expressions_in_selectors [] ti
					= ([],ti)
		# (expr2,ti) = transform expr2 ro ti
		= (Update expr1 selectors expr2,ti)
	transform (RecordUpdate cons_symbol expr exprs) ro ti
		# (expr,ti) = transform expr ro ti
		# (exprs,ti) = transform_fields exprs ro ti
		=(RecordUpdate cons_symbol expr exprs,ti)
	where	
		transform_fields [] ro ti
			= ([],ti)
		transform_fields [bind=:{bind_src} : fields] ro ti
			# (bind_src,ti) = transform bind_src ro ti
			# (fields,ti) = transform_fields fields ro ti
			= ([{bind & bind_src=bind_src} : fields],ti)
	transform (TupleSelect a1 arg_nr expr) ro ti
		# (expr,ti) = transform expr ro ti
		= (TupleSelect a1 arg_nr expr,ti)
	transform (MatchExpr a1 expr) ro ti
		# (expr,ti) = transform expr ro ti
		= (MatchExpr a1 expr,ti)
	transform (DynamicExpr dynamic_expr) ro ti
		# (dynamic_expr, ti) = transform dynamic_expr ro ti
		= (DynamicExpr dynamic_expr, ti)	
	transform expr ro ti
		= (expr, ti)

instance transform DynamicExpr where
	transform dyn=:{dyn_expr} ro ti
		# (dyn_expr, ti) = transform dyn_expr ro ti
		= ({dyn & dyn_expr = dyn_expr}, ti)

transformCase this_case=:{case_expr,case_guards,case_default,case_ident,case_info_ptr} ro ti
	| SwitchCaseFusion (not ro.ro_transform_fusion) True
		= skip_over this_case ro ti
	| isNilPtr case_info_ptr			// encountered neverMatchingCase?!
		= skip_over this_case ro ti
	# (case_info, ti_symbol_heap) = readPtr case_info_ptr ti.ti_symbol_heap
	  ti = { ti & ti_symbol_heap=ti_symbol_heap }
	  (result_expr, ti)	= case case_info of
							EI_Extended (EEI_ActiveCase aci) _
								| is_variable case_expr
									-> skip_over this_case ro ti
								-> case ro.ro_root_case_mode of
									NotRootCase	-> possibly_generate_case_function this_case aci ro ti
									_			-> transCase True (Yes aci) this_case ro ti
							_	-> transCase False No this_case ro ti
	  ti = { ti & ti_symbol_heap = remove_aci_free_vars_info case_info_ptr ti.ti_symbol_heap }
	= (removeNeverMatchingSubcases result_expr ro, ti)
where
	is_variable (Var _) = True
	is_variable _ 		= False

skip_over this_case=:{case_expr,case_guards,case_default} ro ti
	# ro_lost_root = { ro & ro_root_case_mode = NotRootCase }
	  (new_case_expr, ti) = transform case_expr ro_lost_root ti
	  (new_case_guards, ti) = transform case_guards ro_lost_root ti
	  (new_case_default, ti) = transform case_default ro_lost_root ti
	= (Case { this_case & case_expr=new_case_expr, case_guards=new_case_guards, case_default=new_case_default }, ti)

transCase is_active opt_aci this_case=:{case_expr = Case case_in_case} ro ti
	| is_active
		= lift_case case_in_case this_case ro ti
		= skip_over this_case ro ti
where
	lift_case nested_case=:{case_guards,case_default} outer_case ro ti
		| isNilPtr nested_case.case_info_ptr	// neverMatchingCase ?!
			= skip_over outer_case ro ti
		# default_exists = case case_default of
							Yes _	-> True
							No		-> False
		  (case_guards, ti) = lift_patterns default_exists case_guards outer_case ro ti
		  (case_default, ti) = lift_default case_default outer_case ro ti
		  (EI_CaseType outer_case_type, ti_symbol_heap) = readExprInfo outer_case.case_info_ptr ti.ti_symbol_heap
		// the result type of the nested case becomes the result type of the outer case
		  ti_symbol_heap = overwrite_result_type nested_case.case_info_ptr outer_case_type.ct_result_type ti_symbol_heap
		// after this transformation the aci_free_vars information doesn't hold anymore
		  ti_symbol_heap = remove_aci_free_vars_info nested_case.case_info_ptr ti_symbol_heap
		  ti = { ti & ti_symbol_heap = ti_symbol_heap }
		= (Case {nested_case & case_guards = case_guards, case_default = case_default}, ti)
	  where
		overwrite_result_type case_info_ptr new_result_type ti_symbol_heap
			#! (EI_CaseType case_type, ti_symbol_heap)	= readExprInfo case_info_ptr ti_symbol_heap
			= writeExprInfo case_info_ptr (EI_CaseType { case_type & ct_result_type = new_result_type}) ti_symbol_heap

	lift_patterns default_exists (AlgebraicPatterns type case_guards) outer_case ro ti
		# guard_exprs	= [ ap_expr \\ {ap_expr} <- case_guards ]
		# (guard_exprs_with_case, ti) = lift_patterns_2 default_exists guard_exprs outer_case ro ti
		= (AlgebraicPatterns type [ { case_guard & ap_expr=guard_expr } \\ case_guard<-case_guards & guard_expr<-guard_exprs_with_case], ti)
	lift_patterns default_exists (BasicPatterns basic_type case_guards) outer_case ro ti
		# guard_exprs	= [ bp_expr \\ {bp_expr} <- case_guards ]
		# (guard_exprs_with_case, ti) = lift_patterns_2 default_exists guard_exprs outer_case ro ti
		= (BasicPatterns basic_type [ { case_guard & bp_expr=guard_expr } \\ case_guard<-case_guards & guard_expr<-guard_exprs_with_case], ti)
	lift_patterns default_exists (OverloadedListPatterns type decons_expr case_guards) outer_case ro ti
		# guard_exprs	= [ ap_expr \\ {ap_expr} <- case_guards ]
		# (guard_exprs_with_case, ti) = lift_patterns_2 default_exists guard_exprs outer_case ro ti
		= (OverloadedListPatterns type decons_expr [ { case_guard & ap_expr=guard_expr } \\ case_guard<-case_guards & guard_expr<-guard_exprs_with_case], ti)
	lift_patterns _ _ _ _ _
		= abort "lift_patterns does not match"

	lift_patterns_2 False [guard_expr] outer_case ro ti
		// if no default pattern exists, then the outer case expression does not have to be copied for the last pattern
		# (guard_expr, ti)						= possiblyFoldOuterCase True guard_expr outer_case ro ti
		= ([guard_expr], ti)
	lift_patterns_2 default_exists [guard_expr : guard_exprs] outer_case ro ti
		# (guard_expr, ti)						= possiblyFoldOuterCase False guard_expr outer_case ro ti
		  (guard_exprs, ti) = lift_patterns_2 default_exists guard_exprs outer_case ro ti
		= ([guard_expr : guard_exprs], ti)
	lift_patterns_2 _ [] _ _ ti
		= ([], ti)
		
	lift_default (Yes default_expr) outer_case ro ti
		# (default_expr, ti)					= possiblyFoldOuterCase True default_expr outer_case ro ti
		= (Yes default_expr, ti)
	lift_default No _ _ ti
		= (No, ti)

	possiblyFoldOuterCase final guard_expr outer_case ro ti
		| SwitchAutoFoldCaseInCase (isFoldExpression guard_expr) False // otherwise GOTO next alternative
			| False -!-> ("possiblyFoldOuterCase","Case",bef < 0 || act < 0,ro.ro_fun_args,aci.aci_params) = undef
			| bef < 0 || act < 0
				= possiblyFoldOuterCase` final guard_expr outer_case ro ti	//abort "possiblyFoldOuterCase: unexpected!\n"
			= transformApplication { app_symb = folder, app_args = folder_args, app_info_ptr = nilPtr } [] ro ti
		= possiblyFoldOuterCase` final guard_expr outer_case ro ti
	where
		(bef,act)	= ro.ro_fun_geni
		new_f_a_before	= take bef ro.ro_fun_args
		new_f_a_after	= drop (bef+act) ro.ro_fun_args
		
		f_a_before	= new_f_a_before	//| new_f_a_before <> old_f_a_before	= abort "!!!"
		f_a_after	= new_f_a_after

//			= transformApplication { app_symb = folder, app_args = folder_args, app_info_ptr = nilPtr } [] ro ti
//	where
		isFoldExpression (App app)	= isFoldSymbol app.app_symb.symb_kind
		isFoldExpression (Var _)	= True
//		isFoldExpression (Case _)	= True
		isFoldExpression _			= False
		
		isFoldSymbol (SK_Function _)			= True
		isFoldSymbol (SK_LocalMacroFunction _)	= True
		isFoldSymbol (SK_GeneratedFunction _ _)	= True
		isFoldSymbol _							= False
		
		folder		= ro.ro_fun_orig
		folder_args = f_a_before` ++ [guard_expr:f_a_after`]
		old_f_a_before	= takeWhile (\e -> not (isMember e aci.aci_params)) ro.ro_fun_args
		old_f_a_help	= dropWhile (\e -> not (isMember e aci.aci_params)) ro.ro_fun_args
		old_f_a_after	= dropWhile (\e -> isMember e aci.aci_params) old_f_a_help
		f_a_before`	= [Var {var_name = fv_name, var_info_ptr = fv_info_ptr, var_expr_ptr = nilPtr} \\ {fv_name,fv_info_ptr} <- f_a_before]
		f_a_after`	= [Var {var_name = fv_name, var_info_ptr = fv_info_ptr, var_expr_ptr = nilPtr} \\ {fv_name,fv_info_ptr} <- f_a_after]
		(Yes aci)	= opt_aci

		isMember x [hd:tl] = hd.fv_info_ptr==x.fv_info_ptr || isMember x tl
		isMember x []	= False

	possiblyFoldOuterCase` final guard_expr outer_case ro ti
		| final
			= transformCase {outer_case & case_expr = guard_expr} ro ti
		# us = { us_var_heap = ti.ti_var_heap, us_symbol_heap = ti.ti_symbol_heap, us_opt_type_heaps = No
				,us_cleanup_info=ti.ti_cleanup_info, us_local_macro_functions = No }
		  ui									= {ui_handle_aci_free_vars = LeaveThem }
		  (outer_guards, us=:{us_cleanup_info})	= unfold outer_case.case_guards ui us
		  (expr_info, ti_symbol_heap)			= readPtr outer_case.case_info_ptr us.us_symbol_heap
		  (new_info_ptr, ti_symbol_heap)		= newPtr expr_info ti_symbol_heap
		  new_cleanup_info 						= case expr_info of 
		  		EI_Extended _ _
		  			-> [new_info_ptr:us_cleanup_info]
		  		_ 	-> us_cleanup_info
		  ti = { ti & ti_var_heap = us.us_var_heap, ti_symbol_heap = ti_symbol_heap, ti_cleanup_info=new_cleanup_info }
		  new_case								= { outer_case & case_expr = guard_expr, case_guards=outer_guards, case_info_ptr=new_info_ptr }
		= transformCase new_case ro ti
	
transCase is_active opt_aci this_case=:{case_expr = case_expr=:(App app=:{app_symb,app_args}),case_guards,case_default,case_explicit} ro ti
	= case app_symb.symb_kind of
		SK_Constructor cons_index
			| not is_active
				-> skip_over this_case ro ti // XXX currently only active cases are matched at runtime (multimatch problem)
			# algebraicPatterns = getAlgebraicPatterns case_guards
			  aci = case opt_aci of
			  			Yes aci -> aci
			  (may_be_match_expr, ti) = match_and_instantiate aci.aci_linearity_of_patterns cons_index app_args algebraicPatterns case_default ro ti
			-> case may_be_match_expr of
				Yes match_expr
					-> (match_expr, ti)
				No
					-> (neverMatchingCase never_ident, ti) <-!- ("transCase:App:neverMatchingCase",never_ident)
					with
						never_ident = case ro.ro_root_case_mode of
							NotRootCase -> this_case.case_ident
							_ -> Yes ro.ro_fun_case.symb_name
		// otherwise it's a function application
		_	-> case opt_aci of
				Yes aci=:{ aci_params, aci_opt_unfolder }
					-> case aci_opt_unfolder of
						No	-> skip_over this_case ro ti									-!-> ("transCase","No opt unfolder")
						Yes unfolder
							| not (equal app_symb.symb_kind unfolder.symb_kind)
								// in this case a third function could be fused in
								-> possiblyFoldOuterCase this_case ro ti					-!-> ("transCase","Diff opt unfolder",unfolder,app_symb)
							# variables = [ Var {var_name=fv_name, var_info_ptr=fv_info_ptr, var_expr_ptr=nilPtr}
											\\ {fv_name, fv_info_ptr} <- ro.ro_fun_args ]
							  (ti_next_fun_nr, ti) = ti!ti_next_fun_nr						-!-> ("transCase","Yes opt unfolder",unfolder)
							  (new_next_fun_nr, app_symb)
								= case ro.ro_root_case_mode of
										RootCaseOfZombie
											# (ro_fun=:{symb_kind=SK_GeneratedFunction fun_info_ptr _}) = ro.ro_fun_case
											-> (inc ti_next_fun_nr,
											    { ro_fun & symb_kind=SK_GeneratedFunction fun_info_ptr ti_next_fun_nr })
												-!-> ("Recursion","RootCaseOfZombie",ti_next_fun_nr,ti.ti_recursion_introduced)
										RootCase
											-> (ti_next_fun_nr, ro.ro_fun_root)
												-!-> ("Recursion","RootCase",ti_next_fun_nr,ro.ro_fun_root,ti.ti_recursion_introduced)
							  ti = case ro.ro_root_case_mode of
										RootCaseOfZombie
											-> { ti & ti_next_fun_nr = new_next_fun_nr, ti_recursion_introduced = Yes ti_next_fun_nr }
										RootCase
											-> { ti & ti_next_fun_nr = new_next_fun_nr, ti_recursion_introduced = No }
							  app_args1 = replace_arg [ fv_info_ptr \\ {fv_info_ptr}<-aci_params ] app_args variables
							  (app_args2, ti) = transform app_args1 { ro & ro_root_case_mode = NotRootCase } ti
							-> (App {app_symb=app_symb, app_args=app_args2, app_info_ptr=nilPtr}, ti)
				No	-> skip_over this_case ro ti
where
	possiblyFoldOuterCase outer_case ro ti
		| SwitchAutoFoldAppInCase True False
			| False -!-> ("possiblyFoldOuterCase","App",bef < 0 || act < 0,ro.ro_fun_args,aci.aci_params) = undef
			| bef < 0 || act < 0	= skip_over this_case ro ti	//abort "possiblyFoldOuterCase: unexpected!\n"
			= transformApplication { app_symb = folder, app_args = folder_args, app_info_ptr = nilPtr } [] ro ti
		= skip_over this_case ro ti
	where
		(bef,act)	= ro.ro_fun_geni
		new_f_a_before	= take bef ro.ro_fun_args
		new_f_a_after	= drop (bef+act) ro.ro_fun_args
		
		f_a_before	= new_f_a_before
		f_a_after	= new_f_a_after

		folder		= ro.ro_fun_orig
		folder_args = f_a_before` ++ [case_expr:f_a_after`]
		old_f_a_before	= takeWhile (\e -> not (isMember e aci.aci_params)) ro.ro_fun_args
		old_f_a_help	= dropWhile (\e -> not (isMember e aci.aci_params)) ro.ro_fun_args
		old_f_a_after	= dropWhile (\e -> isMember e aci.aci_params) old_f_a_help
		f_a_before`	= [Var {var_name = fv_name, var_info_ptr = fv_info_ptr, var_expr_ptr = nilPtr} \\ {fv_name,fv_info_ptr} <- f_a_before]
		f_a_after`	= [Var {var_name = fv_name, var_info_ptr = fv_info_ptr, var_expr_ptr = nilPtr} \\ {fv_name,fv_info_ptr} <- f_a_after]
		(Yes aci)	= opt_aci

		isMember x [hd:tl] = hd.fv_info_ptr==x.fv_info_ptr || isMember x tl
		isMember x []	= False

	equal (SK_Function glob_index1) (SK_Function glob_index2)
		= glob_index1==glob_index2
	equal (SK_LocalMacroFunction glob_index1) (SK_LocalMacroFunction glob_index2)
		= glob_index1==glob_index2
	equal (SK_GeneratedFunction _ index1) (SK_GeneratedFunction _ index2)
		= index1==index2
	equal _ _
		= False

	replace_arg [] _ f
		= f
	replace_arg producer_vars=:[fv_info_ptr:_] act_pars form_pars=:[h_form_pars=:(Var {var_info_ptr}):t_form_pars]
		| fv_info_ptr<>var_info_ptr
			= [h_form_pars:replace_arg producer_vars act_pars t_form_pars]
		= replacement producer_vars act_pars form_pars
	  where
		replacement producer_vars [] form_pars
			= form_pars
		replacement producer_vars _ []
			= []
		replacement producer_vars [h_act_pars:t_act_pars] [form_par=:(Var {var_info_ptr}):form_pars]
			| isMember var_info_ptr producer_vars
				= [h_act_pars:replacement producer_vars t_act_pars form_pars]
			= replacement producer_vars t_act_pars form_pars

	getAlgebraicPatterns (AlgebraicPatterns _ algebraicPatterns)
		= algebraicPatterns
	getAlgebraicPatterns (OverloadedListPatterns _ _ algebraicPatterns)
		= algebraicPatterns

	match_and_instantiate [linearity:linearities] cons_index app_args 
							[{ap_symbol={glob_module,glob_object={ds_index}}, ap_vars, ap_expr} : guards] 
							case_default ro ti
		| cons_index.glob_module == glob_module && cons_index.glob_object == ds_index
			# zipped = zip2 ap_vars app_args
			  {cons_type} = ro.ro_common_defs.[glob_module].com_cons_defs.[ds_index]
			  unfoldables = [ ((not (arg_is_strict i cons_type.st_args_strictness)) && linear) || in_normal_form app_arg \\ linear <- linearity & app_arg <- app_args & i <- [0..]]
			  unfoldable_args = filterWith unfoldables zipped
			  not_unfoldable = map not unfoldables
			  non_unfoldable_args = filterWith not_unfoldable zipped
			  ti_var_heap = foldSt (\({fv_info_ptr}, arg) -> writeVarInfo fv_info_ptr (VI_Expression arg)) unfoldable_args ti.ti_var_heap
			  (new_expr, ti_symbol_heap) = possibly_add_let non_unfoldable_args ap_expr not_unfoldable cons_type ro ti.ti_symbol_heap
			  unfold_state = { us_var_heap = ti_var_heap, us_symbol_heap = ti_symbol_heap, us_opt_type_heaps = No,us_cleanup_info=ti.ti_cleanup_info,
			  				   us_local_macro_functions = No }
			  ui= {ui_handle_aci_free_vars = LeaveThem }
			  (unfolded_expr, unfold_state) = unfold new_expr ui unfold_state
			  (final_expr, ti) = transform unfolded_expr
			  						{ ro & ro_root_case_mode = NotRootCase }
			  						{ ti & ti_var_heap = unfold_state.us_var_heap, ti_symbol_heap = unfold_state.us_symbol_heap,ti_cleanup_info=unfold_state.us_cleanup_info }
			= (Yes final_expr, ti)
		= match_and_instantiate linearities cons_index app_args guards case_default ro ti
	match_and_instantiate [linearity:linearities] cons_index app_args [guard : guards] case_default ro ti
		= match_and_instantiate linearities cons_index app_args guards case_default ro ti
	match_and_instantiate _ cons_index app_args [] default_expr ro ti
		= transform default_expr { ro & ro_root_case_mode = NotRootCase } ti

transCase is_active opt_aci this_case=:{case_expr = (BasicExpr basic_value),case_guards,case_default} ro ti
	| not is_active
		= skip_over this_case ro ti // XXX currently only active cases are matched at runtime (multimatch problem)
	# basicPatterns = getBasicPatterns case_guards
	  may_be_match_pattern = dropWhile (\{bp_value} -> bp_value<>basic_value) basicPatterns
	| isEmpty may_be_match_pattern
		= case case_default of
			Yes default_expr-> transform default_expr { ro & ro_root_case_mode = NotRootCase } ti
			No				-> (neverMatchingCase never_ident, ti) <-!- ("transCase:BasicExpr:neverMatchingCase",never_ident)
					with
						never_ident = case ro.ro_root_case_mode of
							NotRootCase -> this_case.case_ident
							_ -> Yes ro.ro_fun_case.symb_name
	= transform (hd may_be_match_pattern).bp_expr { ro & ro_root_case_mode = NotRootCase } ti
where
	getBasicPatterns (BasicPatterns _ basicPatterns)
		= basicPatterns

transCase is_active opt_aci this_case=:{case_expr = (Let lad)} ro ti
	| not is_active
		= skip_over this_case ro ti
	# ro_not_root = { ro & ro_root_case_mode = NotRootCase }
	  (new_let_strict_binds, ti) = transform lad.let_strict_binds ro_not_root ti
	  (new_let_lazy_binds, ti) = transform lad.let_lazy_binds ro_not_root ti
	  (new_let_expr, ti) = transform (Case { this_case & case_expr = lad.let_expr }) ro ti
	= (Let { lad & let_expr = new_let_expr, let_strict_binds = new_let_strict_binds, let_lazy_binds = new_let_lazy_binds }, ti)

transCase is_active opt_aci this_case ro ti
	= skip_over this_case ro ti
	
in_normal_form (Var _)			= True
in_normal_form (BasicExpr _)	= True
in_normal_form _				= False

filterWith [True:t2] [h1:t1]
	= [h1:filterWith t2 t1]
filterWith [False:t2] [h1:t1]
	= filterWith t2 t1
filterWith _ _
	= []

possibly_add_let [] ap_expr _ _ _ ti_symbol_heap
	= (ap_expr, ti_symbol_heap)
possibly_add_let non_unfoldable_args ap_expr not_unfoldable cons_type ro ti_symbol_heap
	# let_type = filterWith not_unfoldable cons_type.st_args
	  (new_info_ptr, ti_symbol_heap) = newPtr (EI_LetType let_type) ti_symbol_heap
/* DvA... STRICT_LET
	= ( Let	{	let_strict_binds	= [ {lb_src=lb_src, lb_dst=lb_dst, lb_position = NoPos}
										\\ (lb_dst,lb_src)<-non_unfoldable_args
										& type <- let_type | type.at_annotation == AN_Strict
										]
			,	let_lazy_binds		= [ {lb_src=lb_src, lb_dst=lb_dst, lb_position = NoPos}
										\\ (lb_dst,lb_src)<-non_unfoldable_args
										& type <- let_type | type.at_annotation == AN_None
										]
...DvA */
	= ( Let	{	let_strict_binds	= []
			,	let_lazy_binds		= [ {lb_src=lb_src, lb_dst=lb_dst, lb_position = NoPos}
										\\ (lb_dst,lb_src)<-non_unfoldable_args]
			,	let_expr			= ap_expr
			,	let_info_ptr		= new_info_ptr
			,	let_expr_position	= NoPos
			}
	  , ti_symbol_heap
	  ) 

possibly_generate_case_function :: !Case !ActiveCaseInfo !ReadOnlyTI !*TransformInfo -> *(!Expression, !*TransformInfo)
possibly_generate_case_function kees=:{case_info_ptr} aci=:{aci_free_vars} ro ti=:{ti_recursion_introduced=old_ti_recursion_introduced}
//	| False -!-> ("possibly_generate_case_function",ro.ro_fun_root.symb_name.id_name,ro.ro_fun_case.symb_name.id_name,ro.ro_root_case_mode)
//		= undef
	| not aci.aci_safe
		= skip_over kees ro ti
	// determine free variables
	# ti_var_heap = clearVariables (Case kees) ti.ti_var_heap
	  fvi	= { fvi_var_heap = ti_var_heap, fvi_expr_heap = ti.ti_symbol_heap, fvi_variables = [],
			  fvi_expr_ptrs = ti.ti_cleanup_info }
	  {fvi_var_heap, fvi_expr_heap, fvi_variables, fvi_expr_ptrs}
	  		= freeVariables (Case kees) fvi
	  ti	= { ti & ti_var_heap = fvi_var_heap, ti_symbol_heap = fvi_expr_heap, ti_cleanup_info = fvi_expr_ptrs }
	  free_vars	= fvi_variables
	// search function definition and consumer arguments
	  (outer_fun_def, outer_cons_args, ti_cons_args, ti_fun_defs, ti_fun_heap)
	  		= get_fun_def_and_cons_args ro.ro_fun_root.symb_kind ti.ti_cons_args ti.ti_fun_defs ti.ti_fun_heap
	  outer_arguments
	  		= case outer_fun_def.fun_body of
							TransformedBody {tb_args} 	-> tb_args
							Expanding args				-> args
	  outer_info_ptrs
	  		= [ fv_info_ptr \\ {fv_info_ptr}<-outer_arguments]
	  free_var_info_ptrs
	  		= [ var_info_ptr \\ {var_info_ptr}<-free_vars ]
	  used_mask
	  		= [isMember fv_info_ptr free_var_info_ptrs \\ {fv_info_ptr}<-outer_arguments]
	  arguments_from_outer_fun
	  		= [ outer_argument \\ outer_argument<-outer_arguments & used<-used_mask | used ]
	  lifted_arguments
	  		= [ { fv_def_level = undeff, fv_name = var_name, fv_info_ptr = var_info_ptr, fv_count = undeff}
							\\ {var_name, var_info_ptr} <- free_vars | not (isMember var_info_ptr outer_info_ptrs)]
	  all_args
	  		= lifted_arguments++arguments_from_outer_fun
	| SwitchArityChecks (length all_args > 32) False
		# ti
		  		= { ti & ti_cons_args = ti_cons_args, ti_fun_defs = ti_fun_defs, ti_fun_heap = ti_fun_heap, ti_recursion_introduced = No }
		| ro.ro_transform_fusion
			#  ti	= { ti & ti_error_file = ti.ti_error_file <<< "Possibly missed fusion oppurtunity: Case Arity > 32 " <<< ro.ro_fun_root.symb_name.id_name <<< "\n"}
			= skip_over kees ro ti
		= skip_over kees ro ti
	# (fun_info_ptr, ti_fun_heap)
	  		= newPtr FI_Empty ti_fun_heap
	  fun_ident
	  		= { id_name = ro.ro_fun_root.symb_name.id_name+++"_case", id_info = nilPtr }
	  fun_symb
	  		= { symb_name = fun_ident, symb_kind=SK_GeneratedFunction fun_info_ptr undeff }
	  			<-!- ("<<<transformCaseFunction",fun_ident)
	| SwitchAlwaysIntroduceCaseFunction True False
		# ti
	  		= { ti & ti_cons_args = ti_cons_args, ti_fun_defs = ti_fun_defs, ti_fun_heap = ti_fun_heap }
	  	# fun_index
	  		= ti.ti_next_fun_nr
	  	# ti
	  		= { ti & ti_next_fun_nr = fun_index + 1 }
		# new_ro
	  		= { ro & ro_root_case_mode = RootCaseOfZombie , ro_fun_case = fun_symb, ro_fun_args = all_args }
	  	= generate_case_function fun_index case_info_ptr (Case kees) outer_fun_def outer_cons_args used_mask new_ro ti
	# new_ro
	  		= { ro & ro_root_case_mode = RootCaseOfZombie , ro_fun_case = fun_symb, ro_fun_args = all_args, ro_fun_geni = (-1,-1) }
	  ti
	  		= { ti & ti_cons_args = ti_cons_args, ti_fun_defs = ti_fun_defs, ti_fun_heap = ti_fun_heap, ti_recursion_introduced = No }
	  (new_expr, ti)
	  		= transformCase kees new_ro ti
	  (ti_recursion_introduced, ti)
	  		= ti!ti_recursion_introduced
	  			<-!- ("transformCaseFunction>>>",fun_ident)
	  ti	= { ti & ti_recursion_introduced = old_ti_recursion_introduced }
	= case ti_recursion_introduced of
		Yes fun_index
			-> generate_case_function fun_index case_info_ptr new_expr outer_fun_def outer_cons_args used_mask new_ro ti
		No	-> (new_expr, ti)

generate_case_function :: !Int !ExprInfoPtr !Expression FunDef .ConsClasses [.Bool] !.ReadOnlyTI !*TransformInfo -> (!Expression,!*TransformInfo)
generate_case_function fun_index case_info_ptr new_expr outer_fun_def outer_cons_args used_mask
					{ro_fun_case=ro_fun=:{symb_kind=SK_GeneratedFunction fun_info_ptr _}, ro_fun_args} ti
//	| False -!-> ("generate_case_function",ro_fun.symb_name)		= undef
	# fun_arity								= length ro_fun_args
	# ti = arity_warning "generate_case_function" ro_fun.symb_name fun_index fun_arity ti
	  (Yes {st_vars,st_args,st_attr_env})	= outer_fun_def.fun_type
	  types_from_outer_fun					= [ st_arg \\ st_arg <- st_args & used <- used_mask | used ]
	  nr_of_lifted_vars						= fun_arity-(length types_from_outer_fun)
	  (lifted_types, ti_var_heap)			= mapSt get_type_of_local_var (take nr_of_lifted_vars ro_fun_args) ti.ti_var_heap
	  (EI_CaseType {ct_result_type}, ti_symbol_heap) = readExprInfo case_info_ptr ti.ti_symbol_heap
	  (form_vars, ti_var_heap)				= mapSt bind_to_fresh_expr_var ro_fun_args ti_var_heap

	  arg_types								= lifted_types++types_from_outer_fun

	# ti = {ti & ti_var_heap = ti_var_heap, ti_symbol_heap = ti_symbol_heap}
	# (fun_type,ti)							= determine_case_function_type fun_arity ct_result_type arg_types st_attr_env ti

	  // unfold...
	  us =		{ us_var_heap				= ti.ti_var_heap
	  			, us_symbol_heap			= ti.ti_symbol_heap
	  			, us_opt_type_heaps			= Yes ti.ti_type_heaps
	  			, us_cleanup_info			= ti.ti_cleanup_info
	  			, us_local_macro_functions	= No 
	  			}
	  ui =
	  			{ ui_handle_aci_free_vars	= SubstituteThem
	  			}
	  (copied_expr, us)
			= unfold new_expr ui us
	  {us_var_heap=ti_var_heap, us_symbol_heap=ti_symbol_heap, us_cleanup_info=ti_cleanup_info, us_opt_type_heaps = Yes ti_type_heaps}
	  		= us
	  // generated function...
	  fun_def =	{ fun_symb					= ro_fun.symb_name
				, fun_arity					= fun_arity
				, fun_priority				= NoPrio
				, fun_body					= TransformedBody { tb_args = form_vars, tb_rhs = copied_expr}
				, fun_type					= Yes fun_type
				, fun_pos					= NoPos
				, fun_kind					= FK_Function cNameNotLocationDependent
				, fun_lifted				= undeff
				, fun_info = 	{	fi_calls		= []
								,	fi_group_index	= outer_fun_def.fun_info.fi_group_index
								,	fi_def_level	= NotALevel
								,	fi_free_vars	= []
								,	fi_local_vars	= []
								,	fi_dynamics		= []
// Sjaak: 							,	fi_is_macro_fun = outer_fun_def.fun_info.fi_is_macro_fun
								,	fi_properties	= outer_fun_def.fun_info.fi_properties
								}	
				}
	# cc_args_from_outer_fun		= [ cons_arg \\ cons_arg <- outer_cons_args.cc_args & used <- used_mask | used ]
	  cc_linear_bits_from_outer_fun	= [ cons_arg \\ cons_arg <- outer_cons_args.cc_linear_bits & used <- used_mask | used ]
	  new_cons_args =
	  			{ cc_size			= fun_arity
	  			, cc_args			= repeatn nr_of_lifted_vars CPassive ++ cc_args_from_outer_fun
	  			, cc_linear_bits	= repeatn nr_of_lifted_vars    False ++ cc_linear_bits_from_outer_fun
	  			, cc_producer		= False
	  			}
	  gf =
	  			{ gf_fun_def		= fun_def
	  			, gf_instance_info	= II_Empty
	  			, gf_cons_args		= new_cons_args
	  			, gf_fun_index		= fun_index
	  			}
	  ti_fun_heap = writePtr fun_info_ptr (FI_Function gf) ti.ti_fun_heap
	  ti =
	  			{ ti 
	  			& ti_new_functions	= [fun_info_ptr:ti.ti_new_functions]
	  			, ti_var_heap		= ti_var_heap
	  			, ti_fun_heap		= ti_fun_heap
	  			, ti_symbol_heap	= ti_symbol_heap
	  			, ti_type_heaps		= ti_type_heaps
	  			, ti_cleanup_info	= ti_cleanup_info 
	  			}
	  app_symb = { ro_fun & symb_kind = SK_GeneratedFunction fun_info_ptr fun_index}
	  app_args = map free_var_to_bound_var ro_fun_args
	= ( App {app_symb = app_symb, app_args = app_args, app_info_ptr = nilPtr}, ti)
where
	get_type_of_local_var {fv_info_ptr} var_heap
		# (EVI_VarType a_type, var_heap)	= readExtendedVarInfo fv_info_ptr var_heap
		= (a_type, var_heap)
	free_var_to_bound_var {fv_name, fv_info_ptr}
		= Var { var_name = fv_name, var_info_ptr = fv_info_ptr, var_expr_ptr = nilPtr}
	determine_case_function_type fun_arity ct_result_type arg_types st_attr_env ti
		# {ti_type_heaps}						= ti
		  {th_vars}								= ti_type_heaps
		  (type_variables, th_vars)				= getTypeVars [ct_result_type:arg_types] th_vars
		  (fresh_type_vars, th_vars)			= mapSt bind_to_fresh_type_variable type_variables th_vars
		  ti_type_heaps							= { ti_type_heaps & th_vars = th_vars }
		  (_, fresh_arg_types, ti_type_heaps)	= substitute arg_types ti_type_heaps
		  (_, fresh_result_type, ti_type_heaps)	= substitute ct_result_type ti_type_heaps
		  fun_type =
		  			{ st_vars					= fresh_type_vars
		  			, st_args					= fresh_arg_types
		  			, st_arity					= fun_arity
		  			, st_args_strictness		= NotStrict
		  			, st_result					= fresh_result_type
		  			, st_context				= []
		  			, st_attr_vars				= []
		  			, st_attr_env				= []
		  			}
		  ti									= { ti & ti_type_heaps = ti_type_heaps }
		= (fun_type,ti)

removeNeverMatchingSubcases :: Expression !.ReadOnlyTI -> Expression
removeNeverMatchingSubcases keesExpr=:(Case kees) ro
	// remove those case guards whose right hand side is a never matching case
	| is_never_matching_case keesExpr
		= keesExpr
	# {case_guards, case_default} = kees
	  filtered_default = get_filtered_default case_default
	= case case_guards of
		AlgebraicPatterns i alg_patterns
			| not (any (is_never_matching_case o get_alg_rhs) alg_patterns) && not (is_never_matching_default case_default)
				-> keesExpr // frequent case: all subexpressions can't fail
			# filtered_case_guards = filter (not o is_never_matching_case o get_alg_rhs) alg_patterns
			| has_become_never_matching filtered_default filtered_case_guards
				-> neverMatchingCase never_ident <-!- ("removeNeverMatchingSubcases:AlgebraicPatterns:neverMatchingCase",never_ident)
			| is_default_only filtered_default filtered_case_guards
				-> fromYes case_default
			-> Case {kees & case_guards = AlgebraicPatterns i filtered_case_guards, case_default = filtered_default }
		BasicPatterns bt basic_patterns
			| not (any (is_never_matching_case o get_basic_rhs) basic_patterns) && not (is_never_matching_default case_default)
				-> keesExpr // frequent case: all subexpressions can't fail
			# filtered_case_guards = filter (not o is_never_matching_case o get_basic_rhs) basic_patterns
			| has_become_never_matching filtered_default filtered_case_guards
				-> neverMatchingCase never_ident <-!- ("removeNeverMatchingSubcases:BasicPatterns:neverMatchingCase",never_ident)
			| is_default_only filtered_default filtered_case_guards
				-> fromYes case_default
			-> Case {kees & case_guards = BasicPatterns bt filtered_case_guards, case_default = filtered_default }
		OverloadedListPatterns i decons_expr alg_patterns
			| not (any (is_never_matching_case o get_alg_rhs) alg_patterns) && not (is_never_matching_default case_default)
				-> keesExpr // frequent case: all subexpressions can't fail
			# filtered_case_guards = filter (not o is_never_matching_case o get_alg_rhs) alg_patterns
			| has_become_never_matching filtered_default filtered_case_guards
				-> neverMatchingCase never_ident <-!- ("removeNeverMatchingSubcases:OverloadedListPatterns:neverMatchingCase",never_ident)
			| is_default_only filtered_default filtered_case_guards
				-> fromYes case_default
			-> Case {kees & case_guards = OverloadedListPatterns i decons_expr filtered_case_guards, case_default = filtered_default }
		_	-> abort "removeNeverMatchingSubcases does not match"
where
	get_filtered_default y=:(Yes c_default)
		| is_never_matching_case c_default
			= No
		= y
	get_filtered_default no
		= no
	has_become_never_matching No [] = True
	has_become_never_matching _ _ = False
	is_default_only (Yes _) [] = True
	is_default_only _ _ = False
	is_never_matching_case (Case {case_guards = NoPattern, case_default = No })
		= True
	is_never_matching_case _
		= False
	get_alg_rhs {ap_expr} = ap_expr
	get_basic_rhs {bp_expr} = bp_expr
	is_never_matching_default No
		= False
	is_never_matching_default (Yes expr)
		= is_never_matching_case expr
	never_ident = case ro.ro_root_case_mode of
		NotRootCase -> kees.case_ident
		_ -> Yes ro.ro_fun_case.symb_name
removeNeverMatchingSubcases expr ro
	= expr

	
instance transform LetBind
where
	transform bind=:{lb_src} ro ti
		# (lb_src, ti) = transform lb_src ro ti
		= ({ bind & lb_src = lb_src }, ti)

instance transform BasicPattern
where
	transform pattern=:{bp_expr} ro ti
		# (bp_expr, ti) = transform bp_expr ro ti
		= ({ pattern & bp_expr = bp_expr }, ti)

instance transform AlgebraicPattern
where
	transform pattern=:{ap_expr} ro ti
		# (ap_expr, ti) = transform ap_expr ro ti
		= ({ pattern & ap_expr = ap_expr }, ti)

instance transform CasePatterns
where
	transform (AlgebraicPatterns type patterns) ro ti
		# (patterns, ti) = transform patterns ro ti
		= (AlgebraicPatterns type patterns, ti)
	transform (BasicPatterns type patterns) ro ti
		# (patterns, ti) = transform patterns ro ti
		= (BasicPatterns type patterns, ti)
	transform (OverloadedListPatterns type=:(OverloadedList _ _ _ _) decons_expr patterns) ro ti
		# (patterns, ti) = transform patterns ro ti
		# (decons_expr, ti) = transform decons_expr ro ti
		= (OverloadedListPatterns type decons_expr patterns, ti)
	transform (OverloadedListPatterns type decons_expr patterns) ro ti
		# (patterns, ti) = transform patterns ro ti
		# (decons_expr, ti) = transform decons_expr ro ti
		= (OverloadedListPatterns type decons_expr patterns, ti)
	transform NoPattern ro ti
		= (NoPattern, ti)
	transform _ ro ti
		= abort "transform CasePatterns does not match"

instance transform (Optional a) | transform a
where
	transform (Yes x) ro ti
		# (x, ti) = transform x ro ti
		= (Yes x, ti)
	transform no ro ti
		= (no, ti)

instance transform [a] | transform a
where
	transform [x : xs]  ro ti
		# (x, ti) = transform x ro ti
		  (xs, ti) = transform xs ro ti
		= ([x : xs], ti)
	transform [] ro ti
		= ([], ti)

//@ tryToFindInstance: 

cIsANewFunction		:== True
cIsNotANewFunction	:== False

tryToFindInstance :: !{! Producer} !InstanceInfo !*(Heap FunctionInfo) -> *(!Bool, !FunctionInfoPtr, !InstanceInfo, !.FunctionHeap)
tryToFindInstance new_prods II_Empty fun_heap
	# (fun_def_ptr, fun_heap) = newPtr FI_Empty fun_heap
	= (cIsANewFunction, fun_def_ptr, II_Node new_prods fun_def_ptr II_Empty II_Empty, fun_heap)
tryToFindInstance new_prods instances=:(II_Node prods fun_def_ptr left right) fun_heap
	| size new_prods > size prods
		# (is_new, new_fun_def_ptr, right, fun_heap) = tryToFindInstance new_prods right fun_heap
		= (is_new, new_fun_def_ptr, II_Node prods fun_def_ptr left right, fun_heap)
	| size new_prods < size prods
		# (is_new, new_fun_def_ptr, left, fun_heap) = tryToFindInstance new_prods left fun_heap
		= (is_new, new_fun_def_ptr, II_Node prods fun_def_ptr left right, fun_heap)
	# cmp = compareProducers new_prods prods
	| cmp == Equal
		= (cIsNotANewFunction, fun_def_ptr, instances, fun_heap)
	| cmp == Greater
		# (is_new, new_fun_def_ptr, right, fun_heap) = tryToFindInstance new_prods right fun_heap
		= (is_new, new_fun_def_ptr, II_Node prods fun_def_ptr left right, fun_heap)
		# (is_new, new_fun_def_ptr, left, fun_heap) = tryToFindInstance new_prods left fun_heap
		= (is_new, new_fun_def_ptr, II_Node prods fun_def_ptr left right, fun_heap)

compareProducers prods1 prods2
	#! nr_of_prods = size prods1
	= compare_producers 0 nr_of_prods prods1 prods2
where
	compare_producers prod_index nr_of_prods prods1 prods2
		| prod_index == nr_of_prods
			= Equal
		# cmp = prods1.[prod_index] =< prods2.[prod_index]
		| cmp == Equal
			= compare_producers (inc prod_index) nr_of_prods prods1 prods2
		= cmp

instance =< Producer
where
	(=<) pr1 pr2
		| equal_constructor pr1 pr2
			= compare_constructor_arguments  pr1 pr2
		| less_constructor pr1 pr2
			= Smaller
			= Greater
	where
		compare_constructor_arguments (PR_Function _ _ index1) (PR_Function _ _ index2)
			= index1 =< index2
		compare_constructor_arguments (PR_GeneratedFunction _ _ index1) (PR_GeneratedFunction _ _ index2)
			= index1 =< index2
		compare_constructor_arguments 	(PR_Class app1 lifted_vars_with_types1 t1) 
										(PR_Class app2 lifted_vars_with_types2 t2) 
//			= app1.app_args =< app2.app_args
			# cmp = smallerOrEqual t1 t2
			| cmp<>Equal
				= cmp
			= compare_types lifted_vars_with_types1 lifted_vars_with_types2
		compare_constructor_arguments (PR_Curried symb_ident1 _) (PR_Curried symb_ident2 _)
			= symb_ident1 =< symb_ident2
		compare_constructor_arguments PR_Empty PR_Empty
			= Equal
		compare_constructor_arguments PR_Unused PR_Unused
			= Equal
		compare_constructor_arguments (PR_Constructor symb_ident1 _ _) (PR_Constructor symb_ident2 _ _)
			= symb_ident1 =< symb_ident2
			
		compare_types [(_, type1):types1] [(_, type2):types2]
			# cmp = smallerOrEqual type1 type2
			| cmp<>Equal
				= cmp