erl_parse

The Erlang parser.

This module is the basic Erlang parser that converts tokens into the abstract form of either forms (that is, top-level constructs), expressions, or terms. The Abstract Format is described in the ERTS User's Guide. Notice that a token list must end with the dot token to be acceptable to the parse functions (see the erl_scan(3)) module.

Types

abstract_clause()

Abstract form of an Erlang clause.

abstract_expr()

Abstract form of an Erlang expression.

abstract_form()

Abstract form of an Erlang form.

abstract_type()

Abstract form of an Erlang type.

erl_parse_tree() =
            abstract_clause() |
            abstract_expr() |
            abstract_form() |
            abstract_type()

error_description() = term()

error_info() = {erl_anno:line(), module(), error_description()}

form_info() =
            {eof, erl_anno:line()} |
            {error, erl_scan:error_info() | error_info()} |
            {warning, erl_scan:error_info() | error_info()}

Tuples {error, error_info()} and {warning, error_info()}, denoting syntactically incorrect forms and warnings, and {eof, line()}, denoting an end-of-stream encountered before a complete form had been parsed.

token() = erl_scan:token()

Functions

abstract(Data) -> AbsTerm

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

erl_parse:abstract(T) is equivalent to erl_parse:abstract(T, 0).

abstract(Data, Options) -> AbsTerm

  • encoding_func() = fun((integer() >= 0) -> boolean())

Converts the Erlang data structure Data into an abstract form of type AbsTerm.

Option Line is the line to be assigned to each node of AbsTerm.

Option Encoding is used for selecting which integer lists to be considered as strings. The default is to use the encoding returned by function epp:default_encoding/0. Value none means that no integer lists are considered as strings. encoding_func() is called with one integer of a list at a time; if it returns true for every integer, the list is considered a string.

anno_from_term(Term) -> erl_parse_tree() | form_info()

  • Term = term()

Assumes that Term is a term with the same structure as a erl_parse tree, but with terms, say T, where a erl_parse tree has collections of annotations. Returns a erl_parse tree where each term T is replaced by the value returned by erl_anno:from_term(T). The term Term is traversed in a depth-first, left-to-right fashion.

anno_to_term(Abstr) -> term()

Returns a term where each collection of annotations Anno of the nodes of the erl_parse tree Abstr is replaced by the term returned by erl_anno:to_term(Anno). The erl_parse tree is traversed in a depth-first, left-to-right fashion.

fold_anno(Fun, Acc0, Abstr) -> Acc1

Updates an accumulator by applying Fun on each collection of annotations of the erl_parse tree Abstr. The first call to Fun has AccIn as argument, the returned accumulator AccOut is passed to the next call, and so on. The final value of the accumulator is returned. The erl_parse tree is traversed in a depth-first, left-to-right fashion.

format_error(ErrorDescriptor) -> Chars

Uses an ErrorDescriptor and returns a string that describes the error. This function is usually called implicitly when an ErrorInfo structure is processed (see section Error Information).

map_anno(Fun, Abstr) -> NewAbstr

Modifies the erl_parse tree Abstr by applying Fun on each collection of annotations of the nodes of the erl_parse tree. The erl_parse tree is traversed in a depth-first, left-to-right fashion.

mapfold_anno(Fun, Acc0, Abstr) -> {NewAbstr, Acc1}

Modifies the erl_parse tree Abstr by applying Fun on each collection of annotations of the nodes of the erl_parse tree, while at the same time updating an accumulator. The first call to Fun has AccIn as second argument, the returned accumulator AccOut is passed to the next call, and so on. The modified erl_parse tree and the final value of the accumulator are returned. The erl_parse tree is traversed in a depth-first, left-to-right fashion.

new_anno(Term) -> Abstr

Assumes that Term is a term with the same structure as a erl_parse tree, but with locations where a erl_parse tree has collections of annotations. Returns a erl_parse tree where each location L is replaced by the value returned by erl_anno:new(L). The term Term is traversed in a depth-first, left-to-right fashion.

normalise(AbsTerm) -> Data

Converts the abstract form AbsTerm of a term into a conventional Erlang data structure (that is, the term itself). This function is the inverse of abstract/1.

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

Parses Tokens as if it was a list of expressions. Returns one of the following:

{ok, ExprList}

The parsing was successful. ExprList is a list of the abstract forms of the parsed expressions.
{error, ErrorInfo}

An error occurred.

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

Parses Tokens as if it was a form. Returns one of the following:

{ok, AbsForm}

The parsing was successful. AbsForm is the abstract form of the parsed form.
{error, ErrorInfo}

An error occurred.

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

Parses Tokens as if it was a term. Returns one of the following:

{ok, Term}

The parsing was successful. Term is the Erlang term corresponding to the token list.
{error, ErrorInfo}

An error occurred.

tokens(AbsTerm) -> Tokens

tokens(AbsTerm, MoreTokens) -> Tokens

Generates a list of tokens representing the abstract form AbsTerm of an expression. Optionally, MoreTokens is appended.

Error Information

ErrorInfo is the standard ErrorInfo structure that is returned from all I/O modules. The format is as follows:

{ErrorLine, Module, ErrorDescriptor}

A string describing the error is obtained with the following call:

Module:format_error(ErrorDescriptor)

See Also

erl_anno(3), erl_scan(3), io(3), section The Abstract Format in the ERTS User's Guide