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cerl(3)			   Erlang Module Definition		       cerl(3)

NAME
       cerl - Core Erlang abstract syntax trees.

DESCRIPTION
       Core Erlang abstract syntax trees.

       This  module defines an abstract	data type for representing Core	Erlang
       source code as syntax trees.

       A recommended starting point for	the first-time user is the  documenta-
       tion of the function type/1.

       NOTES:

       This  module  deals with	the composition	and decomposition of syntactic
       entities	(as opposed to semantic	ones); its purpose is to hide all  di-
       rect  references	 to  the data structures used to represent these enti-
       ties. With few exceptions, the functions	in this	module perform no  se-
       mantic  interpretation of their inputs, and in general, the user	is as-
       sumed to	pass type-correct arguments - if this is not done, the effects
       are not defined.

       Currently,  the internal	data structure used is the same	as the record-
       based data structures used traditionally	in the Beam compiler.

       The internal representations of abstract	syntax trees  are  subject  to
       change  without	notice,	and should not be documented outside this mod-
       ule. Furthermore, we do not give	any guarantees on how an abstract syn-
       tax  tree may or	may not	be represented,	with the following exceptions:
       no syntax tree is represented by	a single atom, such as none, by	a list
       constructor  [X	|  Y],	or by the empty	list []. This can be relied on
       when writing functions that operate on syntax trees.

DATA TYPES
	 c_alias() = #c_alias{}:

	 c_apply() = #c_apply{}:

	 c_binary() = #c_binary{}:

	 c_bitstr() = #c_bitstr{}:

	 c_call() = #c_call{}:

	 c_case() = #c_case{}:

	 c_catch() = #c_catch{}:

	 c_clause() = #c_clause{}:

	 c_cons() = #c_cons{}:

	 c_fun() = #c_fun{}:

	 c_lct() = c_literal() | c_cons() | c_tuple():

	 c_let() = #c_let{}:

	 c_letrec() = #c_letrec{}:

	 c_literal() = #c_literal{}:

	 c_map() = #c_map{}:

	 c_map_pair() =	#c_map_pair{}:

	 c_module() = #c_module{}:

	 c_primop() = #c_primop{}:

	 c_receive() = #c_receive{}:

	 c_seq() = #c_seq{}:

	 c_try() = #c_try{}:

	 c_tuple() = #c_tuple{}:

	 c_values() = #c_values{}:

	 c_var() = #c_var{}:

	 cerl()	= c_alias() | c_apply()	| c_binary() | c_bitstr() | c_call() |
	 c_case()  |  c_catch()	 | c_clause() |	c_cons() | c_fun() | c_let() |
	 c_letrec() | c_literal() | c_map()  |	c_map_pair()  |	 c_module()  |
	 c_primop() | c_receive() | c_seq() | c_try() |	c_tuple() | c_values()
	 | c_var():

	 ctype() = alias | apply | binary | bitstr | call |  case  |  catch  |
	 clause	 | cons	| fun |	let | letrec | literal | map | map_pair	| mod-
	 ule | primop |	receive	| seq |	try | tuple | values | var:

	 dtype() = cons	| tuple	| {atomic, value()}:

	 map_op() = #c_literal{val=assoc} | #c_literal{val=exact}:

	 value() = integer() | float() | atom()	| []:

	 var_name() = integer()	| atom() | {atom(), integer()}:

EXPORTS
       abstract(T::term()) -> c_literal()

	      Creates a	syntax tree corresponding to an	Erlang term. Term must
	      be a literal term, i.e., one that	can be represented as a	source
	      code literal. Thus, it may not  contain  a  process  identifier,
	      port, reference, binary or function value	as a subterm.

	      Note: This is a constant time operation.

	      See  also:  ann_abstract/2,  concrete/1,	is_literal/1,  is_lit-
	      eral_term/1.

       add_ann(Terms::[term()],	Node::cerl()) -> cerl()

	      Appends Annotations to the list of user annotations of Node.

	      Note:  this  is  equivalent  to  set_ann(Node,  Annotations   ++
	      get_ann(Node)), but potentially more efficient.

	      See also:	get_ann/1, set_ann/2.

       alias_pat(Node::c_alias()) -> cerl()

	      Returns the pattern subtree of an	abstract pattern alias.

	      See also:	c_alias/2.

       alias_var(Node::c_alias()) -> c_var()

	      Returns the variable subtree of an abstract pattern alias.

	      See also:	c_alias/2.

       ann_abstract(As::[term()], T::term()) ->	c_literal()

	      See also:	abstract/1.

       ann_c_alias(As::[term()], Var::c_var(), Pattern::cerl())	-> c_alias()

	      See also:	c_alias/2.

       ann_c_apply(As::[term()],   Operator::cerl(),  Arguments::[cerl()])  ->
       c_apply()

	      See also:	c_apply/2.

       ann_c_atom(As::[term()],	Name::atom() | string()) -> c_literal()

	      See also:	c_atom/1.

       ann_c_binary(As::[term()], Segments::[cerl()]) -> c_binary()

	      See also:	c_binary/1.

       ann_c_bitstr(As::[term()], Value::cerl(),  Size::cerl(),	 Type::cerl(),
       Flags::cerl()) -> c_bitstr()

	      Equivalent  to  ann_c_bitstr(As, Value, Size, abstract(1), Type,
	      Flags).

       ann_c_bitstr(As::[term()],  Val::cerl(),	 Size::cerl(),	 Unit::cerl(),
       Type::cerl(), Flags::cerl()) -> c_bitstr()

	      See also:	ann_c_bitstr/5,	c_bitstr/5.

       ann_c_call(As::[term()],	    Module::cerl(),	Name::cerl(),	 Argu-
       ments::[cerl()])	-> c_call()

	      See also:	c_call/3.

       ann_c_case(As::[term()],	Expr::cerl(), Clauses::[cerl()]) -> c_case()

	      See also:	c_case/2.

       ann_c_catch(As::[term()], Body::cerl()) -> c_catch()

	      See also:	c_catch/1.

       ann_c_char(As::[term()],	Value::char()) -> c_literal()

	      See also:	c_char/1.

       ann_c_clause(As::[term()],   Patterns::[cerl()],	   Body::cerl())    ->
       c_clause()

	      Equivalent to ann_c_clause(As, Patterns, c_atom(true), Body).

	      See also:	c_clause/3.

       ann_c_clause(As::[term()],      Patterns::[cerl()],	Guard::cerl(),
       Body::cerl()) ->	c_clause()

	      See also:	ann_c_clause/3,	c_clause/3.

       ann_c_cons(As::[term()],	 C_literal::cerl(),  Tail::cerl())  ->	c_lit-
       eral() |	c_cons()

	      See also:	c_cons/2.

       ann_c_cons_skel(As::[term()], Head::cerl(), Tail::cerl()) -> c_cons()

	      See also:	c_cons_skel/2.

       ann_c_float(As::[term()], Value::float()) -> c_literal()

	      See also:	c_float/1.

       ann_c_fname(As::[term()], Atom::atom(), Arity::arity()) -> c_var()

	      Equivalent to ann_c_var(As, {Atom, Arity}).

	      See also:	c_fname/2.

       ann_c_fun(As::[term()], Variables::[cerl()], Body::cerl()) -> c_fun()

	      See also:	c_fun/2.

       ann_c_int(As::[term()], Value::integer()) -> c_literal()

	      See also:	c_int/1.

       ann_c_let(As::[term()],	    Variables::[cerl()],     Argument::cerl(),
       Body::cerl()) ->	c_let()

	      See also:	c_let/3.

       ann_c_letrec(As::[term()], Defs::[{cerl(), cerl()}],  Body::cerl())  ->
       c_letrec()

	      See also:	c_letrec/2.

       ann_c_map(As::[term()], Es::[c_map_pair()]) -> c_map() |	c_literal()

       ann_c_map(As::[term()],	    C_literal::c_map()	    |	  c_literal(),
       Es::[c_map_pair()]) -> c_map() |	c_literal()

       ann_c_map_pair(As::[term()],  Op::cerl(),  K::cerl(),   V::cerl())   ->
       c_map_pair()

       ann_c_map_pattern(As::[term()], Pairs::[c_map_pair()]) -> c_map()

       ann_c_module(As::[term()],	Name::cerl(),	    Exports::[cerl()],
       Es::[{cerl(), cerl()}]) -> c_module()

	      See also:	ann_c_module/5,	c_module/3.

       ann_c_module(As::[term()],   Name::cerl(),    Exports::[cerl()],	   At-
       trs::[{cerl(), cerl()}],	Es::[{cerl(), cerl()}])	-> c_module()

	      See also:	ann_c_module/4,	c_module/4.

       ann_c_nil(As::[term()]) -> c_literal()

	      See also:	c_nil/0.

       ann_c_primop(As::[term()], Name::cerl(),	Arguments::[cerl()]) ->	c_pri-
       mop()

	      See also:	c_primop/2.

       ann_c_receive(As::[term()], Clauses::[cerl()]) -> c_receive()

	      Equivalent  to  ann_c_receive(As,	  Clauses,   c_atom(infinity),
	      c_atom(true)).

	      See also:	c_atom/1, c_receive/3.

       ann_c_receive(As::[term()],   Clauses::[cerl()],	 Timeout::cerl(),  Ac-
       tion::cerl()) ->	c_receive()

	      See also:	ann_c_receive/2, c_receive/3.

       ann_c_seq(As::[term()], Argument::cerl(), Body::cerl()) -> c_seq()

	      See also:	c_seq/2.

       ann_c_string(As::[term()], Value::string()) -> c_literal()

	      See also:	c_string/1.

       ann_c_try(As::[term()],	 Expr::cerl(),	 Vs::[cerl()],	 Body::cerl(),
       Evs::[cerl()], Handler::cerl()) -> c_try()

	      See also:	c_try/5.

       ann_c_tuple(As::[term()], Es::[cerl()]) -> c_tuple() | c_literal()

	      See also:	c_tuple/1.

       ann_c_tuple_skel(As::[term()], Es::[cerl()]) -> c_tuple()

	      See also:	c_tuple_skel/1.

       ann_c_values(As::[term()], Es::[cerl()])	-> c_values()

	      See also:	c_values/1.

       ann_c_var(As::[term()], Name::var_name()) -> c_var()

	      See also:	c_var/1.

       ann_make_data(As::[term()], X2::dtype(),	Es::[cerl()]) -> c_lct()

	      See also:	make_data/2.

       ann_make_data_skel(As::[term()],	X2::dtype(), Es::[cerl()]) -> c_lct()

	      See also:	make_data_skel/2.

       ann_make_list(As::[term()], List::[cerl()]) -> cerl()

	      Equivalent to ann_make_list(As, List, none).

       ann_make_list(As::[term()], T::[cerl()],	Tail::cerl() | none) ->	cerl()

	      See also:	ann_make_list/2, make_list/2.

       ann_make_tree(As::[term()], X2::ctype(),	X3::[[cerl()], ...]) ->	cerl()

	      Creates  a syntax	tree with the given annotations, type and sub-
	      trees. See make_tree/2 for details.

	      See also:	make_tree/2.

       apply_args(Node::c_apply()) -> [cerl()]

	      Returns the list of argument subtrees of	an  abstract  function
	      application.

	      See also:	apply_arity/1, c_apply/2.

       apply_arity(Node::c_apply()) -> arity()

	      Returns  the number of argument subtrees of an abstract function
	      application.

	      Note: this is equivalent to length(apply_args(Node)), but	poten-
	      tially more efficient.

	      See also:	apply_args/1, c_apply/2.

       apply_op(Node::c_apply()) -> cerl()

	      Returns  the  operator  subtree of an abstract function applica-
	      tion.

	      See also:	c_apply/2.

       atom_lit(Node::cerl()) -> nonempty_string()

	      Returns the literal string represented by	an abstract atom. This
	      always includes surrounding single-quote characters.

	      Note  that an abstract atom may have several literal representa-
	      tions, and that the representation yielded by this  function  is
	      not  fixed;  e.g.,  atom_lit(c_atom("a\012b"))  could  yield the
	      string "\'a\\nb\'".

	      See also:	c_atom/1.

       atom_name(Node::c_literal()) -> string()

	      Returns the printname of an abstract atom.

	      See also:	c_atom/1.

       atom_val(Node::c_literal()) -> atom()

	      Returns the value	represented by an abstract atom.

	      See also:	c_atom/1.

       binary_segments(Node::c_binary()) -> [cerl()]

	      Returns the list of segment subtrees of an abstract  binary-tem-
	      plate.

	      See also:	c_binary/1, c_bitstr/5.

       bitstr_bitsize(Node::c_bitstr())	-> all | any | utf | non_neg_integer()

	      Returns  the  total  size	in bits	of an abstract bit-string tem-
	      plate. If	the size field is an integer literal,  the  result  is
	      the  product  of	the size and unit values; if the size field is
	      the atom literal all, the	atom all is returned. If the  size  is
	      not a literal, the atom any is returned.

	      See also:	c_bitstr/5.

       bitstr_flags(Node::c_bitstr()) -> cerl()

	      Returns the flags	subtree	of an abstract bit-string template.

	      See also:	c_bitstr/5.

       bitstr_size(Node::c_bitstr()) ->	cerl()

	      Returns the size subtree of an abstract bit-string template.

	      See also:	c_bitstr/5.

       bitstr_type(Node::c_bitstr()) ->	cerl()

	      Returns the type subtree of an abstract bit-string template.

	      See also:	c_bitstr/5.

       bitstr_unit(Node::c_bitstr()) ->	cerl()

	      Returns the unit subtree of an abstract bit-string template.

	      See also:	c_bitstr/5.

       bitstr_val(Node::c_bitstr()) -> cerl()

	      Returns the value	subtree	of an abstract bit-string template.

	      See also:	c_bitstr/5.

       c_alias(Var::c_var(), Pattern::cerl()) -> c_alias()

	      Creates  an abstract pattern alias. The result represents	"Vari-
	      able = Pattern".

	      See also:	alias_pat/1, alias_var/1,  ann_c_alias/3,  c_clause/3,
	      is_c_alias/1, update_c_alias/3.

       c_apply(Operator::cerl(), Arguments::[cerl()]) -> c_apply()

	      Creates  an  abstract function application. If Arguments is [A1,
	      ..., An],	the result represents "apply Operator(A1, ..., An)".

	      See  also:  ann_c_apply/3,  apply_args/1,	  apply_arity/1,   ap-
	      ply_op/1,	c_call/3, c_primop/2, is_c_apply/1, update_c_apply/3.

       c_atom(Name::atom() | string()) -> c_literal()

	      Creates  an abstract atom	literal. The print name	of the atom is
	      the character sequence represented by Name.

	      Note: passing a string as	argument to  this  function  causes  a
	      corresponding  atom  to  be created for the internal representa-
	      tion.

	      See also:	 ann_c_atom/2,	atom_lit/1,  atom_name/1,  atom_val/1,
	      is_c_atom/1.

       c_binary(Segments::[cerl()]) -> c_binary()

	      Creates  an abstract binary-template. A binary object is in this
	      context a	sequence of an arbitrary number	of bits.  (The	number
	      of  bits	used to	be evenly divisible by 8, but after the	intro-
	      duction of bit strings in	the Erlang language,  the  choice  was
	      made  to	use  the  binary  template for all bit strings.) It is
	      specified	by zero	or more	bit-string template segments of	 arbi-
	      trary lengths (in	number of bits). If Segments is	[S1, ..., Sn],
	      the result represents "#{S1, ...,	Sn}#". All the	Si  must  have
	      type bitstr.

	      See   also:   ann_c_binary/2,   binary_segments/1,   c_bitstr/5,
	      is_c_binary/1, update_c_binary/2.

       c_bitstr(Val::cerl(), Type::cerl(), Flags::cerl()) -> c_bitstr()

	      Equivalent to c_bitstr(Value, abstract(all), abstract(1),	 Type,
	      Flags).

       c_bitstr(Val::cerl(),  Size::cerl(),  Type::cerl(),  Flags::cerl())  ->
       c_bitstr()

	      Equivalent to c_bitstr(Value, Size, abstract(1), Type, Flags).

       c_bitstr(Val::cerl(),   Size::cerl(),	Unit::cerl(),	 Type::cerl(),
       Flags::cerl()) -> c_bitstr()

	      Creates an abstract bit-string template. These can only occur as
	      components of an abstract	binary-template	(see c_binary/1).  The
	      result  represents  "#_Value_(Size,  Unit,  Type,	Flags)", where
	      Unit must	represent a positive integer constant, Type must  rep-
	      resent a constant	atom (one of 'integer',	'float', or 'binary'),
	      and Flags	must represent a constant list "[F1, ...,  Fn]"	 where
	      all the Fi are atoms.

	      See  also:  ann_c_bitstr/6,  bitstr_flags/1, bitstr_size/1, bit-
	      str_type/1, bitstr_unit/1, bitstr_val/1,	c_binary/1,  is_c_bit-
	      str/1, update_c_bitstr/6.

       c_call(Module::cerl(), Name::cerl(), Arguments::[cerl()]) -> c_call()

	      Creates an abstract inter-module call. If	Arguments is [A1, ...,
	      An], the result represents "call Module:Name(A1, ..., An)".

	      See  also:  ann_c_call/4,	 c_apply/2,  c_primop/2,  call_args/1,
	      call_arity/1,   call_module/1,   call_name/1,  is_c_call/1,  up-
	      date_c_call/4.

       c_case(Expr::cerl(), Clauses::[cerl()]) -> c_case()

	      Creates an abstract case-expression. If  Clauses	is  [C1,  ...,
	      Cn],  the	 result	 represents  "case Argument of C1 ... Cn end".
	      Clauses must not be empty.

	      See also:	ann_c_case/3,  c_clause/3,  case_arg/1,	 case_arity/1,
	      case_clauses/1, is_c_case/1, update_c_case/3.

       c_catch(Body::cerl()) ->	c_catch()

	      Creates  an  abstract  catch-expression.	The  result represents
	      "catch Body".

	      Note: catch-expressions can be rewritten as try-expressions, and
	      will eventually be removed from Core Erlang.

	      See  also:  ann_c_catch/2,  c_try/5, catch_body/1, is_c_catch/1,
	      update_c_catch/2.

       c_char(Value::non_neg_integer())	-> c_literal()

	      Creates an abstract character literal. If	the local  implementa-
	      tion  of	Erlang	defines	 char()	as a subset of integer(), this
	      function is equivalent to	c_int/1. Otherwise, if the given value
	      is  an  integer,	it will	be converted to	the character with the
	      corresponding code. The lexical representation of	a character is
	      "$Char",	where Char is a	single printing	character or an	escape
	      sequence.

	      See  also:  ann_c_char/2,	  c_int/1,   c_string/1,   char_lit/1,
	      char_val/1, is_c_char/1, is_print_char/1.

       c_clause(Patterns::[cerl()], Body::cerl()) -> c_clause()

	      Equivalent to c_clause(Patterns, c_atom(true), Body).

	      See also:	c_atom/1.

       c_clause(Patterns::[cerl()], Guard::cerl(), Body::cerl()) -> c_clause()

	      Creates an an abstract clause. If	Patterns is [P1, ..., Pn], the
	      result represents	"_P1, ..., Pn_ when Guard -_ Body".

	      See also:	 ann_c_clause/4,  c_case/2,  c_clause/2,  c_receive/3,
	      clause_arity/1,  clause_body/1,  clause_guard/1,	clause_pats/1,
	      clause_vars/1, is_c_clause/1, update_c_clause/4.

       c_cons(C_literal::cerl(), Tail::cerl()) -> c_literal() |	c_cons()

	      Creates an abstract  list	 constructor.  The  result  represents
	      "[Head  |	Tail]".	Note that if both Head and Tail	have type lit-
	      eral, then the result will also have type	literal,  and  annota-
	      tions on Head and	Tail are lost.

	      Recall that in Erlang, the tail element of a list	constructor is
	      not necessarily a	list.

	      See  also:  ann_c_cons/3,	 c_cons_skel/2,	 c_nil/0,   cons_hd/1,
	      cons_tl/1,     is_c_cons/1,     is_c_list/1,    list_elements/1,
	      list_length/1, make_list/2, update_c_cons/3.

       c_cons_skel(Head::cerl(), Tail::cerl()) -> c_cons()

	      Creates an abstract list constructor  skeleton.  Does  not  fold
	      constant literals, i.e., the result always has type cons,	repre-
	      senting "[Head | Tail]".

	      This function is occasionally useful when	 it  is	 necessary  to
	      have  annotations	 on  the  subnodes of a	list constructor node,
	      even when	the subnodes are constant literals. Note however  that
	      is_literal/1 will	yield false and	concrete/1 will	fail if	passed
	      the result from this function.

	      fold_literal/1 can be used to revert a node to  the  normal-form
	      representation.

	      See  also:  ann_c_cons_skel/3,  c_cons/2,	 c_nil/0,  concrete/1,
	      fold_literal/1,  is_c_cons/1,  is_c_list/1,  is_literal/1,   up-
	      date_c_cons_skel/3.

       c_float(Value::float()) -> c_literal()

	      Creates  an  abstract floating-point literal. The	lexical	repre-
	      sentation	is the decimal floating-point numeral of Value.

	      See also:	ann_c_float/2, float_lit/1, float_val/1, is_c_float/1.

       c_fname(Atom::atom(), Arity::arity()) ->	c_var()

	      Equivalent to c_var({Name, Arity}).

	      See    also:    ann_c_fname/3,	fname_arity/1,	   fname_id/1,
	      is_c_fname/1, update_c_fname/3.

       c_fun(Variables::[cerl()], Body::cerl())	-> c_fun()

	      Creates  an  abstract  fun-expression. If	Variables is [V1, ...,
	      Vn], the result represents "fun (V1, ...,	Vn) -_ Body". All  the
	      Vi must have type	var.

	      See  also:  ann_c_fun/3,	fun_arity/1,  fun_body/1,  fun_vars/1,
	      is_c_fun/1, update_c_fun/3.

       c_int(Value::integer()) -> c_literal()

	      Creates an abstract integer literal. The lexical	representation
	      is the canonical decimal numeral of Value.

	      See   also:   ann_c_int/2,   c_char/1,   int_lit/1,   int_val/1,
	      is_c_int/1.

       c_let(Variables::[cerl()], Argument::cerl(), Body::cerl()) -> c_let()

	      Creates an abstract let-expression. If Variables	is  [V1,  ...,
	      Vn],  the	 result	 represents  "let  _V1,	..., Vn_ = Argument in
	      Body". All the Vi	must have type var.

	      See  also:  ann_c_let/4,	is_c_let/1,  let_arg/1,	  let_arity/1,
	      let_body/1, let_vars/1, update_c_let/4.

       c_letrec(Defs::[{cerl(),	cerl()}], Body::cerl())	-> c_letrec()

	      Creates  an  abstract letrec-expression. If Definitions is [{V1,
	      F1}, ...,	{Vn, Fn}], the result represents "letrec V1 =  F1  ...
	      Vn  =  Fn	 in  Body. All the Vi must have	type var and represent
	      function names. All the Fi must have type	'fun'.

	      See  also:  ann_c_letrec/3,  is_c_letrec/1,  letrec_body/1,  le-
	      trec_defs/1, letrec_vars/1, update_c_letrec/3.

       c_map(Pairs::[c_map_pair()]) -> c_map()

       c_map_pair(Key::cerl(), Val::cerl()) -> c_map_pair()

       c_map_pair_exact(Key::cerl(), Val::cerl()) -> c_map_pair()

       c_map_pattern(Pairs::[c_map_pair()]) -> c_map()

       c_module(Name::cerl(),  Exports::[cerl()],  Es::[{cerl(),  cerl()}]) ->
       c_module()

	      Equivalent to c_module(Name, Exports, [],	Definitions).

       c_module(Name::cerl(),  Exports::[cerl()],  Attrs::[{cerl(),  cerl()}],
       Es::[{cerl(), cerl()}]) -> c_module()

	      Creates an abstract module definition. The result	represents

		  module Name [E1, ...,	Ek]
		    attributes [K1 = T1, ...,
				Km = Tm]
		    V1 = F1
		    ...
		    Vn = Fn
		  end

	      if  Exports  =  [E1, ...,	Ek], Attributes	= [{K1,	T1}, ..., {Km,
	      Tm}], and	Definitions = [{V1, F1}, ..., {Vn, Fn}].

	      Name and all the Ki must be atom literals, and all the  Ti  must
	      be  constant  literals. All the Vi and Ei	must have type var and
	      represent	function names.	All the	Fi must	have type 'fun'.

	      See also:	 ann_c_module/4,  ann_c_module/5,  c_atom/1,  c_fun/2,
	      c_module/3,    c_var/1,	is_literal/1,	module_attrs/1,	  mod-
	      ule_defs/1, module_exports/1, module_name/1, module_vars/1,  up-
	      date_c_module/5.

       c_nil() -> c_literal()

	      Creates  an abstract empty list. The result represents "[]". The
	      empty list is traditionally called "nil".

	      See also:	ann_c_nil/1, c_cons/2, is_c_list/1.

       c_primop(Name::cerl(), Arguments::[cerl()]) -> c_primop()

	      Creates an abstract primitive operation call.  If	 Arguments  is
	      [A1, ...,	An], the result	represents "primop Name(A1, ..., An)".
	      Name must	be an atom literal.

	      See also:	ann_c_primop/3,	 c_apply/2,  c_call/3,	is_c_primop/1,
	      primop_args/1, primop_arity/1, primop_name/1, update_c_primop/3.

       c_receive(Clauses::[cerl()]) -> c_receive()

	      Equivalent      to      c_receive(Clauses,     c_atom(infinity),
	      c_atom(true)).

	      See also:	c_atom/1.

       c_receive(Clauses::[cerl()], Timeout::cerl(), Action::cerl()) ->	 c_re-
       ceive()

	      Creates  an abstract receive-expression. If Clauses is [C1, ...,
	      Cn], the result represents "receive C1 ... Cn after  Timeout  -_
	      Action end".

	      See  also:  ann_c_receive/4,  c_receive/1,  is_c_receive/1,  re-
	      ceive_action/1,	receive_clauses/1,   receive_timeout/1,	   up-
	      date_c_receive/4.

       c_seq(Argument::cerl(), Body::cerl()) ->	c_seq()

	      Creates an abstract sequencing expression. The result represents
	      "do Argument Body".

	      See also:	ann_c_seq/3, is_c_seq/1,  seq_arg/1,  seq_body/1,  up-
	      date_c_seq/3.

       c_string(Value::string()) -> c_literal()

	      Creates  an  abstract  string literal. Equivalent	to creating an
	      abstract list  of	 the  corresponding  character	literals  (cf.
	      is_c_string/1),  but  is	typically  more	efficient. The lexical
	      representation of	a string is ""Chars"", where Chars  is	a  se-
	      quence of	printing characters or spaces.

	      See     also:	ann_c_string/2,	   c_char/1,	is_c_string/1,
	      is_print_string/1, string_lit/1, string_val/1.

       c_try(Expr::cerl(),  Vs::[cerl()],  Body::cerl(),  Evs::[cerl()],  Han-
       dler::cerl()) ->	c_try()

	      Creates  an  abstract  try-expression. If	Variables is [V1, ...,
	      Vn] and ExceptionVars is [X1, ..., Xm],  the  result  represents
	      "try  Argument  of  _V1, ..., Vn_	-_ Body	catch _X1, ...,	Xm_ -_
	      Handler".	All the	Vi and Xi must have type var.

	      See  also:  ann_c_try/6,	 c_catch/1,   is_c_try/1,   try_arg/1,
	      try_body/1, try_vars/1, update_c_try/6.

       c_tuple(Es::[cerl()]) ->	c_tuple() | c_literal()

	      Creates an abstract tuple. If Elements is	[E1, ..., En], the re-
	      sult represents "{E1, ..., En}". Note that if all	nodes in  Ele-
	      ments  have  type	literal, or if Elements	is empty, then the re-
	      sult will	also have type literal and annotations on nodes	in El-
	      ements are lost.

	      Recall  that  Erlang  has	distinct 1-tuples, i.e., {X} is	always
	      distinct from X itself.

	      See also:	ann_c_tuple/2, c_tuple_skel/1, is_c_tuple/1, tuple_ar-
	      ity/1, tuple_es/1, update_c_tuple/2.

       c_tuple_skel(Es::[cerl()]) -> c_tuple()

	      Creates  an abstract tuple skeleton. Does	not fold constant lit-
	      erals, i.e., the result  always  has  type  tuple,  representing
	      "{E1, ..., En}", if Elements is [E1, ...,	En].

	      This  function  is  occasionally	useful when it is necessary to
	      have annotations on the subnodes of a tuple node,	even when  all
	      the  subnodes  are  constant literals. Note however that is_lit-
	      eral/1 will yield	false and concrete/1 will fail if  passed  the
	      result from this function.

	      fold_literal/1  can  be used to revert a node to the normal-form
	      representation.

	      See also:	ann_c_tuple_skel/2, c_tuple/1,	concrete/1,  fold_lit-
	      eral/1,  is_c_tuple/1,  is_literal/1,  tuple_es/1,  update_c_tu-
	      ple_skel/2.

       c_values(Es::[cerl()]) -> c_values()

	      Creates an abstract value	list. If Elements is  [E1,  ...,  En],
	      the result represents "_E1, ..., En_".

	      See also:	ann_c_values/2,	is_c_values/1, update_c_values/2, val-
	      ues_arity/1, values_es/1.

       c_var(Name::var_name()) -> c_var()

	      Creates an abstract variable. A variable is  identified  by  its
	      name, given by the Name parameter.

	      If a name	is given by a single atom, it should either be a "sim-
	      ple" atom	which does not need to be single-quoted	in Erlang,  or
	      otherwise	 its  print  name should correspond to a proper	Erlang
	      variable,	i.e., begin with an uppercase character	or  an	under-
	      score.  Names  on	 the form {A, N} represent function name vari-
	      ables "A/N"; these are special variables which may be bound only
	      in  the  function	 definitions of	a module or a letrec. They may
	      not be bound in let expressions and cannot occur in clause  pat-
	      terns.  The atom A in a function name may	be any atom; the inte-
	      ger N must be nonnegative.  The  functions  c_fname/2  etc.  are
	      utilities	for handling function name variables.

	      When  printing variable names, they must have the	form of	proper
	      Core Erlang variables and	function names.	E.g.,  a  name	repre-
	      sented  by an integer such as 42 could be	formatted as "_42", an
	      atom 'Xxx' simply	as "Xxx", and an atom foo as "_foo".  However,
	      one  must	 assure	 that  any  two	valid distinct names are never
	      mapped to	the same strings. Tuples such as {foo, 2} representing
	      function	names  can  simply  by formatted as "'foo'/2", with no
	      risk of conflicts.

	      See  also:  ann_c_var/2,	c_fname/2,   c_letrec/2,   c_module/4,
	      is_c_var/1, update_c_var/2, var_name/1.

       call_args(Node::c_call()) -> [cerl()]

	      Returns  the list	of argument subtrees of	an abstract inter-mod-
	      ule call.

	      See also:	c_call/3, call_arity/1.

       call_arity(Node::c_call()) -> arity()

	      Returns the number of argument subtrees of  an  abstract	inter-
	      module call.

	      Note:  this is equivalent	to length(call_args(Node)), but	poten-
	      tially more efficient.

	      See also:	c_call/3, call_args/1.

       call_module(Node::c_call()) -> cerl()

	      Returns the module subtree of an abstract	inter-module call.

	      See also:	c_call/3.

       call_name(Node::c_call()) -> cerl()

	      Returns the name subtree of an abstract inter-module call.

	      See also:	c_call/3.

       case_arg(Node::c_case())	-> cerl()

	      Returns the argument subtree of an abstract case-expression.

	      See also:	c_case/2.

       case_arity(Node::c_case()) -> non_neg_integer()

	      Equivalent to clause_arity(hd(case_clauses(Node))),  but	poten-
	      tially more efficient.

	      See also:	c_case/2, case_clauses/1, clause_arity/1.

       case_clauses(Node::c_case()) -> [cerl()]

	      Returns  the list	of clause subtrees of an abstract case-expres-
	      sion.

	      See also:	c_case/2, case_arity/1.

       catch_body(Node::c_catch()) -> cerl()

	      Returns the body subtree of an abstract catch-expression.

	      See also:	c_catch/1.

       char_lit(Node::c_literal()) -> nonempty_string()

	      Returns the literal string represented by	an abstract character.
	      This  includes  a	leading	$ character. Currently,	all characters
	      that are not in the set of ISO 8859-1 (Latin-1) "printing" char-
	      acters will be escaped.

	      See also:	c_char/1.

       char_val(Node::c_literal()) -> char()

	      Returns the value	represented by an abstract character literal.

	      See also:	c_char/1.

       clause_arity(Node::c_clause()) -> non_neg_integer()

	      Returns the number of pattern subtrees of	an abstract clause.

	      Note:  this  is equivalent to length(clause_pats(Node)), but po-
	      tentially	more efficient.

	      See also:	c_clause/3, clause_pats/1.

       clause_body(Node::c_clause()) ->	cerl()

	      Returns the body subtree of an abstract clause.

	      See also:	c_clause/3.

       clause_guard(Node::c_clause()) -> cerl()

	      Returns the guard	subtree	of an abstract clause.

	      See also:	c_clause/3.

       clause_pats(Node::c_clause()) ->	[cerl()]

	      Returns the list of pattern subtrees of an abstract clause.

	      See also:	c_clause/3, clause_arity/1.

       clause_vars(Clause::c_clause()) -> [cerl()]

	      Returns the list of all abstract variables in the	patterns of an
	      abstract clause. The order of listing is not defined.

	      See also:	c_clause/3, pat_list_vars/1.

       concrete(C_literal::c_literal())	-> term()

	      Returns  the Erlang term represented by a	syntax tree. An	excep-
	      tion is thrown if	Node does not represent	a literal term.

	      Note: This is a constant time operation.

	      See also:	abstract/1, is_literal/1.

       cons_hd(C_cons::c_cons()	| c_literal()) -> cerl()

	      Returns the head subtree of an abstract list constructor.

	      See also:	c_cons/2.

       cons_tl(C_cons::c_cons()	| c_literal()) -> cerl()

	      Returns the tail subtree of an abstract list constructor.

	      Recall that the tail does	not  necessarily  represent  a	proper
	      list.

	      See also:	c_cons/2.

       copy_ann(Source::cerl(),	Target::cerl())	-> cerl()

	      Copies the list of user annotations from Source to Target.

	      Note:  this  is  equivalent to set_ann(Target, get_ann(Source)),
	      but potentially more efficient.

	      See also:	get_ann/1, set_ann/2.

       data_arity(C_literal::c_lct()) -> non_neg_integer()

	      Returns the number of subtrees of	a data constructor node.  This
	      is equivalent to length(data_es(Node)), but potentially more ef-
	      ficient.

	      See also:	data_es/1, is_data/1.

       data_es(C_literal::c_lct()) -> [cerl()]

	      Returns the list of subtrees of a	data constructor node. If  the
	      arity of the constructor is zero,	the result is the empty	list.

	      Note:  if	data_type(Node)	is cons, the number of subtrees	is ex-
	      actly two. If data_type(Node) is {atomic,	Value},	the number  of
	      subtrees is zero.

	      See also:	data_arity/1, data_type/1, is_data/1, make_data/2.

       data_type(C_literal::c_lct()) ->	dtype()

	      Returns  a  type	descriptor  for	 a data	constructor node. (Cf.
	      is_data/1.) This is mainly useful	for comparing  types  and  for
	      constructing  new	 nodes	of the same type (cf. make_data/2). If
	      Node represents an integer, floating-point number, atom or empty
	      list, the	result is {atomic, Value}, where Value is the value of
	      concrete(Node), otherwise	the result is either cons or tuple.

	      Type descriptors can be compared for equality or order  (in  the
	      Erlang  term  order),  but  remember  that floating-point	values
	      should in	general	never be tested	for equality.

	      See also:	concrete/1, is_data/1, make_data/2, type/1.

       float_lit(Node::c_literal()) -> string()

	      Returns the numeral string represented by	a floating-point  lit-
	      eral node.

	      See also:	c_float/1.

       float_val(Node::c_literal()) -> float()

	      Returns the value	represented by a floating-point	literal	node.

	      See also:	c_float/1.

       fname_arity(C_var::c_var()) -> arity()

	      Returns the arity	part of	an abstract function name variable.

	      See also:	c_fname/2, fname_id/1.

       fname_id(C_var::c_var())	-> atom()

	      Returns  the  identifier part of an abstract function name vari-
	      able.

	      See also:	c_fname/2, fname_arity/1.

       fold_literal(Node::cerl()) -> cerl()

	      Assures that literals have a compact representation. This	is oc-
	      casionally   useful  if  c_cons_skel/2,  c_tuple_skel/1  or  un-
	      fold_literal/1 were used in the construction of  Node,  and  you
	      want  to	revert to the normal "folded" representation of	liter-
	      als. If Node represents a	tuple or list  constructor,  its  ele-
	      ments  are  rewritten recursively, and the node is reconstructed
	      using c_cons/2 or	c_tuple/1, respectively;  otherwise,  Node  is
	      not changed.

	      See  also:  c_cons/2,  c_cons_skel/2, c_tuple/1, c_tuple_skel/1,
	      is_literal/1, unfold_literal/1.

       from_records(Node::cerl()) -> cerl()

	      Translates an explicit record representation to a	 corresponding
	      abstract	syntax	tree.  The  records  are  defined  in the file
	      "core_parse.hrl".

	      See also:	to_records/1, type/1.

       fun_arity(Node::c_fun())	-> arity()

	      Returns the number of parameter subtrees of an abstract  fun-ex-
	      pression.

	      Note:  this  is equivalent to length(fun_vars(Node)), but	poten-
	      tially more efficient.

	      See also:	c_fun/2, fun_vars/1.

       fun_body(Node::c_fun()) -> cerl()

	      Returns the body subtree of an abstract fun-expression.

	      See also:	c_fun/2.

       fun_vars(Node::c_fun()) -> [cerl()]

	      Returns the list of parameter subtrees of	 an  abstract  fun-ex-
	      pression.

	      See also:	c_fun/2, fun_arity/1.

       get_ann(Node::cerl()) ->	[term()]

	      Returns  the  list  of user annotations associated with a	syntax
	      tree node. For a newly created node, this	is the empty list. The
	      annotations may be any terms.

	      See also:	set_ann/2.

       int_lit(Node::c_literal()) -> string()

	      Returns  the  numeral  string  represented by an integer literal
	      node.

	      See also:	c_int/1.

       int_val(Node::c_literal()) -> integer()

	      Returns the value	represented by an integer literal node.

	      See also:	c_int/1.

       is_c_alias(C_alias::cerl()) -> boolean()

	      Returns true if Node is an  abstract  pattern  alias,  otherwise
	      false.

	      See also:	c_alias/2.

       is_c_apply(C_apply::cerl()) -> boolean()

	      Returns true if Node is an abstract function application,	other-
	      wise false.

	      See also:	c_apply/2.

       is_c_atom(C_literal::cerl()) -> boolean()

	      Returns true if  Node  represents	 an  atom  literal,  otherwise
	      false.

	      See also:	c_atom/1.

       is_c_binary(C_binary::cerl()) ->	boolean()

	      Returns  true  if	Node is	an abstract binary-template; otherwise
	      false.

	      See also:	c_binary/1.

       is_c_bitstr(C_bitstr::cerl()) ->	boolean()

	      Returns true if Node is an abstract bit-string template;	other-
	      wise false.

	      See also:	c_bitstr/5.

       is_c_call(C_call::cerl()) -> boolean()

	      Returns  true  if	 Node is an abstract inter-module call expres-
	      sion; otherwise false.

	      See also:	c_call/3.

       is_c_case(C_case::cerl()) -> boolean()

	      Returns true if Node is an abstract  case-expression;  otherwise
	      false.

	      See also:	c_case/2.

       is_c_catch(C_catch::cerl()) -> boolean()

	      Returns  true if Node is an abstract catch-expression, otherwise
	      false.

	      See also:	c_catch/1.

       is_c_char(C_literal::c_literal()) -> boolean()

	      Returns true if Node may represent a character  literal,	other-
	      wise false.

	      If the local implementation of Erlang defines char() as a	subset
	      of integer(), then is_c_int(Node)	will also yield	true.

	      See also:	c_char/1, is_print_char/1.

       is_c_clause(C_clause::cerl()) ->	boolean()

	      Returns true if Node is an abstract clause, otherwise false.

	      See also:	c_clause/3.

       is_c_cons(C_cons::cerl()) -> boolean()

	      Returns true if Node is an abstract list constructor,  otherwise
	      false.

       is_c_float(C_literal::cerl()) ->	boolean()

	      Returns true if Node represents a	floating-point literal,	other-
	      wise false.

	      See also:	c_float/1.

       is_c_fname(C_var::cerl()) -> boolean()

	      Returns true if Node is an abstract function name	variable, oth-
	      erwise false.

	      See also:	c_fname/2, c_var/1, var_name/1.

       is_c_fun(C_fun::cerl()) -> boolean()

	      Returns  true  if	 Node is an abstract fun-expression, otherwise
	      false.

	      See also:	c_fun/2.

       is_c_int(C_literal::cerl()) -> boolean()

	      Returns true if Node represents an  integer  literal,  otherwise
	      false.

	      See also:	c_int/1.

       is_c_let(C_let::cerl()) -> boolean()

	      Returns  true  if	 Node is an abstract let-expression, otherwise
	      false.

	      See also:	c_let/3.

       is_c_letrec(C_letrec::cerl()) ->	boolean()

	      Returns true if Node is an abstract letrec-expression, otherwise
	      false.

	      See also:	c_letrec/2.

       is_c_list(C_cons::cerl()) -> boolean()

	      Returns  true if Node represents a proper	list, otherwise	false.
	      A	proper list is either the empty	list [], or a cons cell	 [Head
	      |	Tail], where recursively Tail is a proper list.

	      Note:  Because Node is a syntax tree, the	actual run-time	values
	      corresponding to its subtrees may	often  be  partially  or  com-
	      pletely  unknown.	 Thus,	if  Node  represents e.g. "[...	| Ns]"
	      (where Ns	is a variable),	then the function will	return	false,
	      because  it  is  not known whether Ns will be bound to a list at
	      run-time.	If Node	instead	represents e.g.	"[1, 2,	3]" or	"[A  |
	      []]", then the function will return true.

	      See also:	c_cons/2, c_nil/0, list_elements/1, list_length/1.

       is_c_map(C_map::cerl()) -> boolean()

	      Returns  true  if	Node is	an abstract map	constructor, otherwise
	      false.

       is_c_map_empty(C_map::c_map() | c_literal()) -> boolean()

       is_c_map_pattern(C_map::c_map())	-> boolean()

       is_c_module(C_module::cerl()) ->	boolean()

	      Returns true if Node is an abstract module definition, otherwise
	      false.

	      See also:	type/1.

       is_c_nil(C_literal::cerl()) -> boolean()

	      Returns true if Node is an abstract empty	list, otherwise	false.

       is_c_primop(C_primop::cerl()) ->	boolean()

	      Returns  true  if	 Node is an abstract primitive operation call,
	      otherwise	false.

	      See also:	c_primop/2.

       is_c_receive(C_receive::cerl()) -> boolean()

	      Returns true if Node is an abstract  receive-expression,	other-
	      wise false.

	      See also:	c_receive/3.

       is_c_seq(C_seq::cerl()) -> boolean()

	      Returns  true if Node is an abstract sequencing expression, oth-
	      erwise false.

	      See also:	c_seq/2.

       is_c_string(C_literal::cerl()) -> boolean()

	      Returns true if Node may represent a string  literal,  otherwise
	      false.   Strings	 are  defined  as  lists  of  characters;  see
	      is_c_char/1 for details.

	      See also:	c_string/1, is_c_char/1, is_print_string/1.

       is_c_try(C_try::cerl()) -> boolean()

	      Returns true if Node is an  abstract  try-expression,  otherwise
	      false.

	      See also:	c_try/5.

       is_c_tuple(C_tuple::cerl()) -> boolean()

	      Returns true if Node is an abstract tuple, otherwise false.

	      See also:	c_tuple/1.

       is_c_values(C_values::cerl()) ->	boolean()

	      Returns true if Node is an abstract value	list; otherwise	false.

	      See also:	c_values/1.

       is_c_var(C_var::cerl()) -> boolean()

	      Returns true if Node is an abstract variable, otherwise false.

	      See also:	c_var/1.

       is_data(C_literal::cerl()) -> boolean()

	      Returns  true  if	 Node represents a data	constructor, otherwise
	      false. Data constructors are cons	cells, tuples, and atomic lit-
	      erals.

	      See also:	data_arity/1, data_es/1, data_type/1.

       is_leaf(Node::cerl()) ->	boolean()

	      Returns  true  if	Node is	a leaf node, otherwise false. The cur-
	      rent leaf	node types are literal and var.

	      Note: all	literals (cf. is_literal/1) are	leaf  nodes,  even  if
	      they  represent structured (constant) values such	as {foo, [bar,
	      baz]}. Also note that variables are leaf nodes but not literals.

	      See also:	is_literal/1, type/1.

       is_literal(C_literal::cerl()) ->	boolean()

	      Returns true if Node represents a	literal	term, otherwise	false.
	      This  function  returns  true  if	 and only if the value of con-
	      crete(Node) is defined.

	      Note: This is a constant time operation.

	      See also:	abstract/1, concrete/1,	fold_literal/1.

       is_literal_term(T::term()) -> boolean()

	      Returns true if Term can be represented as a literal,  otherwise
	      false.  This  function  takes  time  proportional	to the size of
	      Term.

	      See also:	abstract/1.

       is_print_char(C_literal::cerl())	-> boolean()

	      Returns true if Node may represent a "printing" character,  oth-
	      erwise  false. (Cf. is_c_char/1.)	A "printing" character has ei-
	      ther a given graphical representation, or	a "named"  escape  se-
	      quence  such as "\n". Currently, only ISO	8859-1 (Latin-1) char-
	      acter values are recognized.

	      See also:	c_char/1, is_c_char/1.

       is_print_string(C_literal::cerl()) -> boolean()

	      Returns true if Node may represent a string  literal  containing
	      only  "printing"	characters, otherwise false. See is_c_string/1
	      and is_print_char/1 for  details.	 Currently,  only  ISO	8859-1
	      (Latin-1)	character values are recognized.

	      See also:	c_string/1, is_c_string/1, is_print_char/1.

       let_arg(Node::c_let()) -> cerl()

	      Returns the argument subtree of an abstract let-expression.

	      See also:	c_let/3.

       let_arity(Node::c_let())	-> non_neg_integer()

	      Returns  the  number  of left-hand side variables	of an abstract
	      let-expression.

	      Note: this is equivalent to length(let_vars(Node)),  but	poten-
	      tially more efficient.

	      See also:	c_let/3, let_vars/1.

       let_body(Node::c_let()) -> cerl()

	      Returns the body subtree of an abstract let-expression.

	      See also:	c_let/3.

       let_vars(Node::c_let()) -> [cerl()]

	      Returns the list of left-hand side variables of an abstract let-
	      expression.

	      See also:	c_let/3, let_arity/1.

       letrec_body(Node::c_letrec()) ->	cerl()

	      Returns the body subtree of an abstract letrec-expression.

	      See also:	c_letrec/2.

       letrec_defs(Node::c_letrec()) ->	[{cerl(), cerl()}]

	      Returns the list of definitions of  an  abstract	letrec-expres-
	      sion.  If	 Node represents "letrec V1 = F1 ... Vn	= Fn in	Body",
	      the returned value is [{V1, F1}, ..., {Vn, Fn}].

	      See also:	c_letrec/2.

       letrec_vars(Node::c_letrec()) ->	[cerl()]

	      Returns the list of left-hand side function variable subtrees of
	      a	letrec-expression. If Node represents "letrec V1 = F1 ... Vn =
	      Fn in Body", the returned	value is [V1, ..., Vn].

	      See also:	c_letrec/2.

       list_elements(C_cons::c_cons() |	c_literal()) ->	[cerl()]

	      Returns the list of element subtrees of an abstract  list.  Node
	      must  represent a	proper list. E.g., if Node represents "[X1, X2
	      |	[X3, X4	| []]",	then list_elements(Node) yields	the list  [X1,
	      X2, X3, X4].

	      See   also:   c_cons/2,	c_nil/0,  is_c_list/1,	list_length/1,
	      make_list/2.

       list_length(L::c_cons() | c_literal()) -> non_neg_integer()

	      Returns the number of element subtrees of	an abstract list. Node
	      must  represent  a  proper list. E.g., if	Node represents	"[X1 |
	      [X2, X3 |	[X4, X5, X6]]]", then  list_length(Node)  returns  the
	      integer 6.

	      Note: this is equivalent to length(list_elements(Node)), but po-
	      tentially	more efficient.

	      See also:	c_cons/2, c_nil/0, is_c_list/1,	list_elements/1.

       make_data(CType::dtype(), Es::[cerl()]) -> c_lct()

	      Creates a	data constructor node with the specified type and sub-
	      trees.  (Cf.  data_type/1.) An exception is thrown if the	length
	      of Elements is invalid for the given Type; see data_es/1 for ar-
	      ity constraints on constructor types.

	      See     also:	ann_make_data/3,    data_es/1,	  data_type/1,
	      make_data_skel/2,	update_data/3.

       make_data_skel(CType::dtype(), Es::[cerl()]) -> c_lct()

	      Like  make_data/2,   but	 analogous   to	  c_tuple_skel/1   and
	      c_cons_skel/2.

	      See  also:  ann_make_data_skel/3,	c_cons_skel/2, c_tuple_skel/1,
	      make_data/2, update_data_skel/3.

       make_list(List::[cerl()]) -> cerl()

	      Equivalent to make_list(List, none).

       make_list(List::[cerl()], Tail::cerl() |	none) -> cerl()

	      Creates an abstract list from the	elements in List and  the  op-
	      tional  Tail.  If	Tail is	none, the result will represent	a nil-
	      terminated list, otherwise it represents "[... | Tail]".

	      See also:	ann_make_list/3, c_cons/2,  c_nil/0,  list_elements/1,
	      update_list/3.

       make_tree(Type::ctype(),	Gs::[[cerl()], ...]) ->	cerl()

	      Creates  a  syntax  tree	with the given type and	subtrees. Type
	      must be a	node type name (cf. type/1) that  does	not  denote  a
	      leaf  node  type (cf. is_leaf/1).	Groups must be a nonempty list
	      of groups	of syntax trees, representing the subtrees of  a  node
	      of the given type, in left-to-right order	as they	would occur in
	      the printed program text,	grouped	by category as	done  by  sub-
	      trees/1.

	      The  result  of  ann_make_tree(get_ann(Node),  type(Node),  sub-
	      trees(Node)) (cf.	update_tree/2) represents the same source code
	      text as the original Node, assuming that subtrees(Node) yields a
	      nonempty list. However, it does not necessarily have  the	 exact
	      same data	representation as Node.

	      See  also:  ann_make_tree/3,  is_leaf/1, subtrees/1, type/1, up-
	      date_tree/2.

       map_arg(C_literal::c_map() | c_literal()) -> c_map() | c_literal()

       map_es(C_literal::c_map() | c_literal())	-> [c_map_pair()]

       map_pair_key(C_map_pair::c_map_pair()) -> cerl()

       map_pair_op(C_map_pair::c_map_pair()) ->	map_op()

       map_pair_val(C_map_pair::c_map_pair()) -> cerl()

       meta(Node::cerl()) -> cerl()

	      Creates a	meta-representation of a syntax	tree. The result  rep-
	      resents  an  Erlang  expression  "MetaTree" which, if evaluated,
	      will yield a new syntax tree representing	the same  source  code
	      text  as	Tree  (although	 the actual data representation	may be
	      different). The expression represented by	MetaTree is  implemen-
	      tation  independent  with	 regard	to the data structures used by
	      the abstract syntax tree implementation.

	      Any node in Tree whose node type is var (cf. type/1), and	 whose
	      list  of annotations (cf.	get_ann/1) contains the	atom meta_var,
	      will remain unchanged in the resulting tree, except that exactly
	      one occurrence of	meta_var is removed from its annotation	list.

	      The  main	 use  of  the  function	 meta/1	is to transform	a data
	      structure	Tree, which represents a piece of program code,	into a
	      form that	is representation independent when printed. E.g., sup-
	      pose Tree	represents a variable  named  "V".  Then  (assuming  a
	      function	 print/1   for	 printing  syntax  trees),  evaluating
	      print(abstract(Tree)) - simply using abstract/1 to map  the  ac-
	      tual  data  structure  onto a syntax tree	representation - would
	      output a string that  might  look	 something  like  "{var,  ...,
	      'V'}", which is obviously	dependent on the implementation	of the
	      abstract syntax trees. This could	e.g. be	useful for  caching  a
	      syntax  tree  in	a  file. However, in some situations like in a
	      program generator	generator (with	two "generator"),  it  may  be
	      unacceptable.  Using  print(meta(Tree))  instead	would output a
	      representation independent syntax	tree generating	expression; in
	      the above	case, something	like "cerl:c_var('V')".

	      The  implementation  tries to generate compact code with respect
	      to literals and lists.

	      See also:	abstract/1, get_ann/1, type/1.

       module_attrs(Node::c_module()) -> [{cerl(), cerl()}]

	      Returns the list of pairs	of attribute key/value subtrees	of  an
	      abstract module definition.

	      See also:	c_module/4.

       module_defs(Node::c_module()) ->	[{cerl(), cerl()}]

	      Returns  the  list of function definitions of an abstract	module
	      definition.

	      See also:	c_module/4.

       module_exports(Node::c_module())	-> [cerl()]

	      Returns the list of exports subtrees of an abstract module defi-
	      nition.

	      See also:	c_module/4.

       module_name(Node::c_module()) ->	cerl()

	      Returns the name subtree of an abstract module definition.

	      See also:	c_module/4.

       module_vars(Node::c_module()) ->	[cerl()]

	      Returns the list of left-hand side function variable subtrees of
	      an abstract module definition.

	      See also:	c_module/4.

       pat_list_vars(Ps::[cerl()]) -> [cerl()]

	      Returns the list of all abstract variables  in  the  given  pat-
	      terns.  An  exception is thrown if some element in Patterns does
	      not represent a well-formed Core Erlang clause pattern. The  or-
	      der of listing is	not defined.

	      See also:	clause_vars/1, pat_vars/1.

       pat_vars(Node::cerl()) -> [cerl()]

	      Returns  the list	of all abstract	variables in a pattern.	An ex-
	      ception is thrown	if Node	does not represent a well-formed  Core
	      Erlang clause pattern. The order of listing is not defined.

	      See also:	clause_vars/1, pat_list_vars/1.

       primop_args(Node::c_primop()) ->	[cerl()]

	      Returns  the  list of argument subtrees of an abstract primitive
	      operation	call.

	      See also:	c_primop/2, primop_arity/1.

       primop_arity(Node::c_primop()) -> arity()

	      Returns the number of argument subtrees of an abstract primitive
	      operation	call.

	      Note:  this  is equivalent to length(primop_args(Node)), but po-
	      tentially	more efficient.

	      See also:	c_primop/2, primop_args/1.

       primop_name(Node::c_primop()) ->	cerl()

	      Returns the name subtree	of  an	abstract  primitive  operation
	      call.

	      See also:	c_primop/2.

       receive_action(Node::c_receive()) -> cerl()

	      Returns the action subtree of an abstract	receive-expression.

	      See also:	c_receive/3.

       receive_clauses(Node::c_receive()) -> [cerl()]

	      Returns  the  list of clause subtrees of an abstract receive-ex-
	      pression.

	      See also:	c_receive/3.

       receive_timeout(Node::c_receive()) -> cerl()

	      Returns the timeout subtree of an	abstract receive-expression.

	      See also:	c_receive/3.

       seq_arg(Node::c_seq()) -> cerl()

	      Returns the argument subtree of an abstract  sequencing  expres-
	      sion.

	      See also:	c_seq/2.

       seq_body(Node::c_seq()) -> cerl()

	      Returns the body subtree of an abstract sequencing expression.

	      See also:	c_seq/2.

       set_ann(Node::cerl(), List::[term()]) ->	cerl()

	      Sets the list of user annotations	of Node	to Annotations.

	      See also:	add_ann/2, copy_ann/2, get_ann/1.

       string_lit(Node::c_literal()) ->	nonempty_string()

	      Returns  the  literal  string represented	by an abstract string.
	      This includes surrounding	double-quote  characters  "...".  Cur-
	      rently,  characters  that	 are  not  in  the  set	 of ISO	8859-1
	      (Latin-1)	"printing" characters will be escaped, except for spa-
	      ces.

	      See also:	c_string/1.

       string_val(Node::c_literal()) ->	string()

	      Returns the value	represented by an abstract string literal.

	      See also:	c_string/1.

       subtrees(T::cerl()) -> [[cerl()]]

	      Returns the grouped list of all subtrees of a node. If Node is a
	      leaf node	(cf. is_leaf/1), this is the empty list, otherwise the
	      result  is  always a nonempty list, containing the lists of sub-
	      trees of Node, in	left-to-right  order  as  they	occur  in  the
	      printed program text, and	grouped	by category. Often, each group
	      contains only a single subtree.

	      Depending	on the type of Node, the size of some  groups  may  be
	      variable	(e.g.,	the  group consisting of all the elements of a
	      tuple), while others always contain the same number of  elements
	      -	 usually  exactly one (e.g., the group containing the argument
	      expression of a case-expression).	Note, however, that the	 exact
	      structure	of the returned	list (for a given node type) should in
	      general not be depended upon,  since  it	might  be  subject  to
	      change without notice.

	      The   function   subtrees/1   and	  the	constructor  functions
	      make_tree/2 and update_tree/2 can	be a great help	if  one	 wants
	      to  traverse a syntax tree, visiting all its subtrees, but treat
	      nodes of the tree	in a uniform way in most or all	 cases.	 Using
	      these  functions	makes  this simple, and	also assures that your
	      code is not overly sensitive to extensions of  the  syntax  tree
	      data type, because any node types	not explicitly handled by your
	      code can be left to a default case.

	      For example:

		  postorder(F, Tree) ->
		      F(case subtrees(Tree) of
			  [] ->	Tree;
			  List -> update_tree(Tree,
					      [[postorder(F, Subtree)
						|| Subtree <- Group]
					       || Group	<- List])
			end).

	      maps the function	F on Tree and all its subtrees,	doing a	 post-
	      order  traversal	of  the	 syntax	 tree.	(Note  the  use	of up-
	      date_tree/2 to preserve  annotations.)  For  a  simple  function
	      like:

		  f(Node) ->
		      case type(Node) of
			  atom -> atom("a_" ++ atom_name(Node));
			  _ -> Node
		      end.

	      the  call	 postorder(fun f/1, Tree) will yield a new representa-
	      tion of Tree in which all	atom names have	been extended with the
	      prefix  "a_",  but nothing else (including annotations) has been
	      changed.

	      See also:	is_leaf/1, make_tree/2,	update_tree/2.

       to_records(Node::cerl())	-> cerl()

	      Translates an abstract syntax tree to a  corresponding  explicit
	      record  representation.  The  records  are  defined  in the file
	      "cerl.hrl".

	      See also:	from_records/1,	type/1.

       try_arg(Node::c_try()) -> cerl()

	      Returns the expression subtree of	an abstract try-expression.

	      See also:	c_try/5.

       try_body(Node::c_try()) -> cerl()

	      Returns the success body subtree of an abstract try-expression.

	      See also:	c_try/5.

       try_evars(Node::c_try())	-> [cerl()]

	      Returns the list of exception variable subtrees of  an  abstract
	      try-expression.

	      See also:	c_try/5.

       try_handler(Node::c_try()) -> cerl()

	      Returns  the  exception  body subtree of an abstract try-expres-
	      sion.

	      See also:	c_try/5.

       try_vars(Node::c_try()) -> [cerl()]

	      Returns the list of success variable  subtrees  of  an  abstract
	      try-expression.

	      See also:	c_try/5.

       tuple_arity(C_tuple::c_tuple() |	c_literal()) ->	non_neg_integer()

	      Returns the number of element subtrees of	an abstract tuple.

	      Note:  this  is equivalent to length(tuple_es(Node)), but	poten-
	      tially more efficient.

	      See also:	c_tuple/1, tuple_es/1.

       tuple_es(C_tuple::c_tuple() | c_literal()) -> [cerl()]

	      Returns the list of element subtrees of an abstract tuple.

	      See also:	c_tuple/1.

       type(C_alias::cerl()) ->	ctype()

	      Returns the type tag of Node. Current node types are:

	      alias apply binary bitstr	call case catch	clause
	      cons fun let letrec literal map map_pair module
	      primop receive seq try tuple values var

	      Note: The	name of	the primary constructor	function  for  a  node
	      type  is	always	the name of the	type itself, prefixed by "c_";
	      recognizer predicates are	correspondingly	prefixed  by  "is_c_".
	      Furthermore,   to	 simplify  preservation	 of  annotations  (cf.
	      get_ann/1), there	are analogous constructor  functions  prefixed
	      by  "ann_c_" and "update_c_", for	setting	the annotation list of
	      the new node to either a specific	value or to the	annotations of
	      an existing node,	respectively.

	      See  also:  abstract/1, c_alias/2, c_apply/2, c_binary/1,	c_bit-
	      str/5,  c_call/3,	 c_case/2,  c_catch/1,	c_clause/3,  c_cons/2,
	      c_fun/2,	c_let/3,  c_letrec/2,  c_module/3,  c_primop/2,	 c_re-
	      ceive/1,	c_seq/2,  c_try/5,  c_tuple/1,	c_values/1,   c_var/1,
	      data_type/1,   from_records/1,  get_ann/1,  meta/1,  subtrees/1,
	      to_records/1.

       unfold_literal(Node::cerl()) -> cerl()

	      Assures that literals have a fully expanded  representation.  If
	      Node  represents	a  literal tuple or list constructor, its ele-
	      ments are	rewritten recursively, and the node  is	 reconstructed
	      using  c_cons_skel/2 or c_tuple_skel/1, respectively; otherwise,
	      Node is not changed. The fold_literal/1 can be used to revert to
	      the normal compact representation.

	      See  also:  c_cons/2,  c_cons_skel/2, c_tuple/1, c_tuple_skel/1,
	      fold_literal/1, is_literal/1.

       update_c_alias(Node::c_alias(),	 Var::cerl(),	Pattern::cerl())    ->
       c_alias()

	      See also:	c_alias/2.

       update_c_apply(Node::c_apply(),	Operator::cerl(), Arguments::[cerl()])
       -> c_apply()

	      See also:	c_apply/2.

       update_c_binary(Node::c_binary(), Segments::[cerl()]) ->	c_binary()

	      See also:	c_binary/1.

       update_c_bitstr(Node::c_bitstr(),     Value::cerl(),	 Size::cerl(),
       Type::cerl(), Flags::cerl()) -> c_bitstr()

	      Equivalent  to  update_c_bitstr(Node,  Value, Size, abstract(1),
	      Type, Flags).

       update_c_bitstr(Node::c_bitstr(),      Val::cerl(),	 Size::cerl(),
       Unit::cerl(), Type::cerl(), Flags::cerl()) -> c_bitstr()

	      See also:	c_bitstr/5, update_c_bitstr/5.

       update_c_call(Node::cerl(),    Module::cerl(),	 Name::cerl(),	 Argu-
       ments::[cerl()])	-> c_call()

	      See also:	c_call/3.

       update_c_case(Node::c_case(),   Expr::cerl(),   Clauses::[cerl()])   ->
       c_case()

	      See also:	c_case/2.

       update_c_catch(Node::c_catch(), Body::cerl()) ->	c_catch()

	      See also:	c_catch/1.

       update_c_clause(Node::c_clause(),   Patterns::[cerl()],	Guard::cerl(),
       Body::cerl()) ->	c_clause()

	      See also:	c_clause/3.

       update_c_cons(Node::c_literal()	  |    c_cons(),    C_literal::cerl(),
       Tail::cerl()) ->	c_literal() | c_cons()

	      See also:	c_cons/2.

       update_c_cons_skel(Node::c_cons()    |	 c_literal(),	 Head::cerl(),
       Tail::cerl()) ->	c_cons()

	      See also:	c_cons_skel/2.

       update_c_fname(C_var::c_var(), Atom::atom()) -> c_var()

	      Like update_c_fname/3, but takes the arity from Node.

	      See also:	c_fname/2, update_c_fname/3.

       update_c_fname(Node::c_var(), Atom::atom(), Arity::arity()) -> c_var()

	      Equivalent to update_c_var(Old, {Atom, Arity}).

	      See also:	c_fname/2, update_c_fname/2.

       update_c_fun(Node::c_fun(),   Variables::[cerl()],   Body::cerl())   ->
       c_fun()

	      See also:	c_fun/2.

       update_c_let(Node::c_let(),    Variables::[cerl()],   Argument::cerl(),
       Body::cerl()) ->	c_let()

	      See also:	c_let/3.

       update_c_letrec(Node::c_letrec(),       Defs::[{cerl(),	     cerl()}],
       Body::cerl()) ->	c_letrec()

	      See also:	c_letrec/2.

       update_c_map(C_map::c_map(),  M::cerl(),	 Es::[cerl()])	->  c_map()  |
       c_literal()

       update_c_map_pair(Old::c_map_pair(),	 Op::map_op(),	    K::cerl(),
       V::cerl()) -> c_map_pair()

       update_c_module(Node::c_module(),  Name::cerl(),	Exports::[cerl()], At-
       trs::[{cerl(), cerl()}],	Es::[{cerl(), cerl()}])	-> c_module()

	      See also:	c_module/4.

       update_c_primop(Node::cerl(),  Name::cerl(),  Arguments::[cerl()])   ->
       c_primop()

	      See also:	c_primop/2.

       update_c_receive(Node::c_receive(), Clauses::[cerl()], Timeout::cerl(),
       Action::cerl()) -> c_receive()

	      See also:	c_receive/3.

       update_c_seq(Node::c_seq(), Argument::cerl(), Body::cerl()) -> c_seq()

	      See also:	c_seq/2.

       update_c_try(Node::c_try(), Expr::cerl(),  Vs::[cerl()],	 Body::cerl(),
       Evs::[cerl()], Handler::cerl()) -> c_try()

	      See also:	c_try/5.

       update_c_tuple(Node::c_tuple()  |  c_literal(),	Es::[cerl()]) -> c_tu-
       ple() | c_literal()

	      See also:	c_tuple/1.

       update_c_tuple_skel(Old::c_tuple(), Es::[cerl()]) -> c_tuple()

	      See also:	c_tuple_skel/1.

       update_c_values(Node::c_values(), Es::[cerl()]) -> c_values()

	      See also:	c_values/1.

       update_c_var(Node::c_var(), Name::var_name()) ->	c_var()

	      See also:	c_var/1.

       update_data(Node::cerl(), CType::dtype(), Es::[cerl()]) -> c_lct()

	      See also:	make_data/2.

       update_data_skel(Node::cerl(), CType::dtype(), Es::[cerl()]) -> c_lct()

	      See also:	make_data_skel/2.

       update_list(Node::cerl(), List::[cerl()]) -> cerl()

	      Equivalent to update_list(Old, List, none).

       update_list(Node::cerl(),  List::[cerl()],  Tail::cerl()	 |  none)   ->
       cerl()

	      See also:	make_list/2, update_list/2.

       update_tree(Node::cerl(), Gs::[[cerl()],	...]) -> cerl()

	      Creates a	syntax tree with the given subtrees, and the same type
	      and  annotations	as  the	 Old  node.  This  is  equivalent   to
	      ann_make_tree(get_ann(Node),  type(Node),	 Groups),  but	poten-
	      tially more efficient.

	      See also:	ann_make_tree/3, get_ann/1, type/1, update_tree/3.

       update_tree(Node::cerl(), Type::ctype(),	Gs::[[cerl()], ...]) ->	cerl()

	      Creates a	syntax tree with the given type	and subtrees, and  the
	      same  annotations	 as  the  Old  node.  This  is	equivalent  to
	      ann_make_tree(get_ann(Node), Type, Groups), but potentially more
	      efficient.

	      See also:	ann_make_tree/3, get_ann/1, update_tree/2.

       values_arity(Node::c_values()) -> non_neg_integer()

	      Returns  the  number  of	element	 subtrees of an	abstract value
	      list.

	      Note: This is equivalent to length(values_es(Node)), but	poten-
	      tially more efficient.

	      See also:	c_values/1, values_es/1.

       values_es(Node::c_values()) -> [cerl()]

	      Returns the list of element subtrees of an abstract value	list.

	      See also:	c_values/1, values_arity/1.

       var_name(Node::c_var()) -> var_name()

	      Returns the name of an abstract variable.

	      See also:	c_var/1.

AUTHORS
       Richard Carlsson	_carlsson.richard@gmail.com_

				compiler 8.0.3			       cerl(3)

NAME | DESCRIPTION | DATA TYPES | EXPORTS | AUTHORS

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