erl_parse

MODULE

erl_parse

MODULE SUMMARY

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. Note that a token list must end with the dot token in order to be acceptable to the parse functions (see erl_scan).

EXPORTS

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

Types:
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. See section Abstract Form below for a description of AbsForm.


{error, ErrorInfo}

An error occurred.

parse_exprs(Tokens) -> {ok, Expr_list} | {error, ErrorInfo}

Types:
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 form AbsExpr, which is described in the section Abstract Form below.


{error, ErrorInfo}

An error occurred.

parse_term(Tokens) -> {ok, Term} | {error, ErrorInfo}

Types:
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) -> string()

Types:
ErrorDescriptor = errordesc()

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:
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

Types:
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

Types:
Data = AbsTerm = term()

Converts the Erlang data structure Data into an abstract form of type AbsTerm. This is the inverse of normalise/1.

Abstract Form

To be supplied

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:

apply(Module, format_error, ErrorDescriptor)

See Also

io, erl_scan

AUTHORS

Robert Virding - support@erlang.ericsson.se