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NAME
erl_parse - The Erlang Parser
DESCRIPTION
This module is the basic Erlang parser which converts tokens into the abstract form of either forms
(i.e., top-level constructs), expressions, or terms. The Abstract Format is described in the ERTS User's
Guide. Note that a token list must end with the dot token in order to be acceptable to the parse
functions (see erl_scan(3erl)).
DATA TYPES
abstract_clause() = term()
Parse tree for Erlang clause.
abstract_expr() = term()
Parse tree for Erlang expression.
abstract_form() = term()
Parse tree for Erlang form.
error_description() = term()
error_info() = {erl_anno:line(), module(), error_description()}
token() = erl_scan:token()
EXPORTS
parse_form(Tokens) -> {ok, AbsForm} | {error, ErrorInfo}
Types:
Tokens = [token()]
AbsForm = abstract_form()
ErrorInfo = error_info()
This function parses Tokens as if it were a form. It returns:
{ok, AbsForm}:
The parsing was successful. AbsForm is the abstract form of the parsed form.
{error, ErrorInfo}:
An error occurred.
parse_exprs(Tokens) -> {ok, ExprList} | {error, ErrorInfo}
Types:
Tokens = [token()]
ExprList = [abstract_expr()]
ErrorInfo = error_info()
This function parses Tokens as if it were a list of expressions. It returns:
{ok, ExprList}:
The parsing was successful. ExprList is a list of the abstract forms of the parsed
expressions.
{error, ErrorInfo}:
An error occurred.
parse_term(Tokens) -> {ok, Term} | {error, ErrorInfo}
Types:
Tokens = [token()]
Term = term()
ErrorInfo = error_info()
This function parses Tokens as if it were a term. It returns:
{ok, Term}:
The parsing was successful. Term is the Erlang term corresponding to the token list.
{error, ErrorInfo}:
An error occurred.
format_error(ErrorDescriptor) -> Chars
Types:
ErrorDescriptor = error_description()
Chars = [char() | Chars]
Uses an ErrorDescriptor and returns a string which describes the error. This function is usually
called implicitly when an ErrorInfo structure is processed (see below).
tokens(AbsTerm) -> Tokens
tokens(AbsTerm, MoreTokens) -> Tokens
Types:
AbsTerm = abstract_expr()
MoreTokens = Tokens = [token()]
This function generates a list of tokens representing the abstract form AbsTerm of an expression.
Optionally, it appends MoreTokens.
normalise(AbsTerm) -> Data
Types:
AbsTerm = abstract_expr()
Data = term()
Converts the abstract form AbsTerm of a term into a conventional Erlang data structure (i.e., the
term itself). This is the inverse of abstract/1.
abstract(Data) -> AbsTerm
Types:
Data = term()
AbsTerm = abstract_expr()
Converts the Erlang data structure Data into an abstract form of type AbsTerm. This is the inverse
of normalise/1.
erl_parse:abstract(T) is equivalent to erl_parse:abstract(T, 0).
abstract(Data, Options) -> AbsTerm
Types:
Data = term()
Options = Line | [Option]
Option = {line, Line} | {encoding, Encoding}
Encoding = latin1 | unicode | utf8 | none | encoding_func()
Line = erl_anno:line()
AbsTerm = abstract_expr()
encoding_func() = fun((integer() >= 0) -> boolean())
Converts the Erlang data structure Data into an abstract form of type AbsTerm.
The Line option is the line that will be assigned to each node of the abstract form.
The Encoding option is used for selecting which integer lists will be considered as strings. The
default is to use the encoding returned by epp:default_encoding/0. The value none means that no
integer lists will be considered as strings. The encoding_func() will be called with one integer
of a list at a time, and if it returns true for every integer the list will be considered a
string.
map_anno(Fun, Abstr) -> NewAbstr
Types:
Fun = fun((Anno) -> Anno)
Anno = erl_anno:anno()
Abstr = NewAbstr = abstract_form() | abstract_expr()
Modifies the abstract form Abstr by applying Fun on every collection of annotations of the
abstract form. The abstract form is traversed in a depth-first, left-to-right, fashion.
fold_anno(Fun, Acc0, Abstr) -> NewAbstr
Types:
Fun = fun((Anno, AccIn) -> AccOut)
Anno = erl_anno:anno()
Acc0 = AccIn = AccOut = term()
Abstr = NewAbstr = abstract_form() | abstract_expr()
Updates an accumulator by applying Fun on every collection of annotations of the abstract form
Abstr. The first call to Fun has AccIn as argument, and the returned accumulator AccOut is passed
to the next call, and so on. The final value of the accumulator is returned. The abstract form is
traversed in a depth-first, left-to-right, fashion.
mapfold_anno(Fun, Acc0, Abstr) -> {NewAbstr, Acc1}
Types:
Fun = fun((Anno, AccIn) -> {Anno, AccOut})
Anno = erl_anno:anno()
Acc0 = Acc1 = AccIn = AccOut = term()
Abstr = NewAbstr = abstract_form() | abstract_expr()
Modifies the abstract form Abstr by applying Fun on every collection of annotations of the
abstract form, while at the same time updating an accumulator. The first call to Fun has AccIn as
second argument, and the returned accumulator AccOut is passed to the next call, and so on. The
modified abstract form as well as the the final value of the accumulator is returned. The abstract
form is traversed in a depth-first, left-to-right, fashion.
new_anno(Term) -> Abstr
Types:
Term = term()
Abstr = abstract_form() | abstract_expr()
Creates an abstract form from a term which has the same structure as an abstract form, but
locations where the abstract form has annotations. For each location, erl_anno:new/1 is called,
and the annotations replace the location.
anno_from_term(Term) -> abstract_form() | abstract_expr()
Types:
Term = term()
Assumes that Term is a term with the same structure as an abstract form, but with terms, T say, on
those places where an abstract form has annotations. Returns an abstract form where every term T
has been replaced by the value returned by calling erl_anno:from_term(T). The term Term is
traversed in a depth-first, left-to-right, fashion.
anno_to_term(Abstr) -> term()
Types:
Abstr = abstract_form() | abstract_expr()
Returns a term where every collection of annotations Anno of Abstr has been replaced by the term
returned by calling erl_anno:to_term(Anno). The abstract form is traversed in a depth-first, left-
to-right, fashion.
ERROR INFORMATION
The ErrorInfo mentioned above is the standard ErrorInfo structure which is returned from all IO modules.
It has the format:
{ErrorLine, Module, ErrorDescriptor}
A string which describes the error is obtained with the following call:
Module:format_error(ErrorDescriptor)
SEE ALSO
io(3erl), erl_anno(3erl), erl_scan(3erl), ERTS User's Guide
Ericsson AB stdlib 2.8 erl_parse(3erl)