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NAME
erl_parse - The Erlang parser.
DESCRIPTION
This module is the basic Erlang parser that converts tokens into the abstract form of
either forms (that is, top-level constructs), expressions, or terms. The Abstract Format
is described in the ERTS User's Guide. Notice that a token list must end with the dot
token to be acceptable to the parse functions (see the erl_scan(3erl)) module.
DATA TYPES
abstract_clause()
Abstract form of an Erlang clause.
abstract_expr()
Abstract form of an Erlang expression.
abstract_form()
Abstract form of an Erlang form.
abstract_type()
Abstract form of an Erlang type.
erl_parse_tree() =
abstract_clause() |
abstract_expr() |
abstract_form() |
abstract_type()
error_description() = term()
error_info() = {erl_anno:line(), module(), error_description()}
form_info() =
{eof, erl_anno:line()} |
{error, erl_scan:error_info() | error_info()} |
{warning, erl_scan:error_info() | error_info()}
Tuples {error, error_info()} and {warning, error_info()}, denoting syntactically
incorrect forms and warnings, and {eof, line()}, denoting an end-of-stream
encountered before a complete form had been parsed.
token() = erl_scan:token()
EXPORTS
abstract(Data) -> AbsTerm
Types:
Data = term()
AbsTerm = abstract_expr()
Converts the Erlang data structure Data into an abstract form of type AbsTerm. This
function 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.
Option Line is the line to be assigned to each node of AbsTerm.
Option Encoding is used for selecting which integer lists to be considered as
strings. The default is to use the encoding returned by function
epp:default_encoding/0. Value none means that no integer lists are considered as
strings. encoding_func() is called with one integer of a list at a time; if it
returns true for every integer, the list is considered a string.
anno_from_term(Term) -> erl_parse_tree() | form_info()
Types:
Term = term()
Assumes that Term is a term with the same structure as a erl_parse tree, but with
terms, say T, where a erl_parse tree has collections of annotations. Returns a
erl_parse tree where each term T is replaced by the value returned by
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 = erl_parse_tree() | form_info()
Returns a term where each collection of annotations Anno of the nodes of the
erl_parse tree Abstr is replaced by the term returned by erl_anno:to_term(Anno).
The erl_parse tree is traversed in a depth-first, left-to-right fashion.
fold_anno(Fun, Acc0, Abstr) -> Acc1
Types:
Fun = fun((Anno, AccIn) -> AccOut)
Anno = erl_anno:anno()
Acc0 = Acc1 = AccIn = AccOut = term()
Abstr = erl_parse_tree() | form_info()
Updates an accumulator by applying Fun on each collection of annotations of the
erl_parse tree Abstr. The first call to Fun has AccIn as argument, the returned
accumulator AccOut is passed to the next call, and so on. The final value of the
accumulator is returned. The erl_parse tree is traversed in a depth-first, left-to-
right fashion.
format_error(ErrorDescriptor) -> Chars
Types:
ErrorDescriptor = error_description()
Chars = [char() | Chars]
Uses an ErrorDescriptor and returns a string that describes the error. This
function is usually called implicitly when an ErrorInfo structure is processed (see
section Error Information).
map_anno(Fun, Abstr) -> NewAbstr
Types:
Fun = fun((Anno) -> NewAnno)
Anno = NewAnno = erl_anno:anno()
Abstr = NewAbstr = erl_parse_tree() | form_info()
Modifies the erl_parse tree Abstr by applying Fun on each collection of annotations
of the nodes of the erl_parse tree. The erl_parse tree is traversed in a depth-
first, left-to-right fashion.
mapfold_anno(Fun, Acc0, Abstr) -> {NewAbstr, Acc1}
Types:
Fun = fun((Anno, AccIn) -> {NewAnno, AccOut})
Anno = NewAnno = erl_anno:anno()
Acc0 = Acc1 = AccIn = AccOut = term()
Abstr = NewAbstr = erl_parse_tree() | form_info()
Modifies the erl_parse tree Abstr by applying Fun on each collection of annotations
of the nodes of the erl_parse tree, while at the same time updating an accumulator.
The first call to Fun has AccIn as second argument, the returned accumulator AccOut
is passed to the next call, and so on. The modified erl_parse tree and the final
value of the accumulator are returned. The erl_parse tree is traversed in a depth-
first, left-to-right fashion.
new_anno(Term) -> Abstr
Types:
Term = term()
Abstr = erl_parse_tree() | form_info()
Assumes that Term is a term with the same structure as a erl_parse tree, but with
locations where a erl_parse tree has collections of annotations. Returns a
erl_parse tree where each location L is replaced by the value returned by
erl_anno:new(L). The term Term is traversed in a depth-first, left-to-right
fashion.
normalise(AbsTerm) -> Data
Types:
AbsTerm = abstract_expr()
Data = term()
Converts the abstract form AbsTerm of a term into a conventional Erlang data
structure (that is, the term itself). This function is the inverse of abstract/1.
parse_exprs(Tokens) -> {ok, ExprList} | {error, ErrorInfo}
Types:
Tokens = [token()]
ExprList = [abstract_expr()]
ErrorInfo = error_info()
Parses Tokens as if it was a list of expressions. Returns one of the following:
{ok, ExprList}:
The parsing was successful. ExprList is a list of the abstract forms of the
parsed expressions.
{error, ErrorInfo}:
An error occurred.
parse_form(Tokens) -> {ok, AbsForm} | {error, ErrorInfo}
Types:
Tokens = [token()]
AbsForm = abstract_form()
ErrorInfo = error_info()
Parses Tokens as if it was a form. Returns one of the following:
{ok, AbsForm}:
The parsing was successful. AbsForm is the abstract form of the parsed form.
{error, ErrorInfo}:
An error occurred.
parse_term(Tokens) -> {ok, Term} | {error, ErrorInfo}
Types:
Tokens = [token()]
Term = term()
ErrorInfo = error_info()
Parses Tokens as if it was a term. Returns one of the following:
{ok, Term}:
The parsing was successful. Term is the Erlang term corresponding to the token
list.
{error, ErrorInfo}:
An error occurred.
tokens(AbsTerm) -> Tokens
tokens(AbsTerm, MoreTokens) -> Tokens
Types:
AbsTerm = abstract_expr()
MoreTokens = Tokens = [token()]
Generates a list of tokens representing the abstract form AbsTerm of an expression.
Optionally, MoreTokens is appended.
ERROR INFORMATION
ErrorInfo is the standard ErrorInfo structure that is returned from all I/O modules. The
format is as follows:
{ErrorLine, Module, ErrorDescriptor}
A string describing the error is obtained with the following call:
Module:format_error(ErrorDescriptor)
SEE ALSO
erl_anno(3erl), erl_scan(3erl), io(3erl), section The Abstract Format in the ERTS User's
Guide