erl_parse

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erl_parse 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)).

parse_form(Tokens) -> {ok, AbsForm} | {error, ErrorInfo} Parse an Erlang form Tokens = [Token] Token = {Tag,Line} | {Tag,Line,term()} Tag = atom() AbsForm = term() ErrorInfo = see section Error Information below.

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, Expr_list} | {error, ErrorInfo} Parse Erlang expressions Tokens = [Token] Token = {Tag,Line} | {Tag,Line,term()} Tag = atom() Expr_list = [AbsExpr] AbsExpr = term() ErrorInfo = see section Error Information below.

This function parses Tokens as if it were a list of expressions. It returns:

{ok, Expr_list}

The parsing was successful. Expr_list is a list of the abstract forms of the parsed expressions.

{error, ErrorInfo}

An error occurred.

parse_term(Tokens) -> {ok, Term} | {error, ErrorInfo} Parse an Erlang term Tokens = [Token] Token = {Tag,Line} | {Tag,Line,term()} Tag = atom() Term = term() ErrorInfo = see section Error Information below.

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 Format an error descriptor ErrorDescriptor = errordesc() 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 Generate a list of tokens for an expression Tokens = MoreTokens = [Token] Token = {Tag,Line} | {Tag,Line,term()} Tag = atom() AbsTerm = term() ErrorInfo = see section Error Information below.

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

normalise(AbsTerm) -> Data Convert abstract form to an Erlang term AbsTerm = 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 Convert an Erlang term into an abstract form Data = AbsTerm = term()

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)