erl_parse(3)

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(3)).

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() = {Tag :: atom(), Line :: erl_scan:line()}

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.

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(3), erl_scan(3), ERTS User's Guide