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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_scan: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
Line = erl_scan:line()
AbsTerm = abstract_expr()
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
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_scan(3erl), ERTS User's Guide