erl_parse

(stdlib)

The Erlang Parser

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)).

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()}

Functions

parse_form(Tokens) -> {ok, AbsForm} | {error, ErrorInfo}

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}

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}

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

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

This function generates a list of tokens representing the abstract form AbsTerm of an expression. Optionally, it appends MoreTokens.

normalise(AbsTerm) -> Data

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

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