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NAME
epp - An Erlang Code Preprocessor
DESCRIPTION
The Erlang code preprocessor includes functions which are used by compile to preprocess macros and
include files before the actual parsing takes place.
The Erlang source file encoding is selected by a comment in one of the first two lines of the source
file. The first string that matches the regular expression coding\s*[:=]\s*([-a-zA-Z0-9])+ selects the
encoding. If the matching string is not a valid encoding it is ignored. The valid encodings are Latin-1
and UTF-8 where the case of the characters can be chosen freely. Examples:
%% coding: utf-8
%% For this file we have chosen encoding = Latin-1
%% -*- coding: latin-1 -*-
DATA TYPES
macros() = [atom() | {atom(), term()}]
epp_handle() = pid()
Handle to the epp server.
source_encoding() = latin1 | utf8
EXPORTS
open(Options) ->
{ok, Epp} | {ok, Epp, Extra} | {error, ErrorDescriptor}
Types:
Options =
[{default_encoding, DefEncoding :: source_encoding()} |
{includes, IncludePath :: [DirectoryName :: file:name()]} |
{macros, PredefMacros :: macros()} |
{name, FileName :: file:name()} |
extra]
Epp = epp_handle()
Extra = [{encoding, source_encoding() | none}]
ErrorDescriptor = term()
Opens a file for preprocessing.
If extra is given in Options, the return value will be {ok, Epp, Extra} instead of {ok, Epp}.
open(FileName, IncludePath) ->
{ok, Epp} | {error, ErrorDescriptor}
Types:
FileName = file:name()
IncludePath = [DirectoryName :: file:name()]
Epp = epp_handle()
ErrorDescriptor = term()
Equivalent to epp:open([{name, FileName}, {includes, IncludePath}]).
open(FileName, IncludePath, PredefMacros) ->
{ok, Epp} | {error, ErrorDescriptor}
Types:
FileName = file:name()
IncludePath = [DirectoryName :: file:name()]
PredefMacros = macros()
Epp = epp_handle()
ErrorDescriptor = term()
Equivalent to epp:open([{name, FileName}, {includes, IncludePath}, {macros, PredefMacros}]).
close(Epp) -> ok
Types:
Epp = epp_handle()
Closes the preprocessing of a file.
parse_erl_form(Epp) ->
{ok, AbsForm} | {eof, Line} | {error, ErrorInfo}
Types:
Epp = epp_handle()
AbsForm = erl_parse:abstract_form()
Line = erl_anno:line()
ErrorInfo = erl_scan:error_info() | erl_parse:error_info()
Returns the next Erlang form from the opened Erlang source file. The tuple {eof, Line} is returned
at end-of-file. The first form corresponds to an implicit attribute -file(File,1)., where File is
the name of the file.
parse_file(FileName, Options) ->
{ok, [Form]} |
{ok, [Form], Extra} |
{error, OpenError}
Types:
FileName = file:name()
Options =
[{includes, IncludePath :: [DirectoryName :: file:name()]} |
{macros, PredefMacros :: macros()} |
{default_encoding, DefEncoding :: source_encoding()} |
extra]
Form =
erl_parse:abstract_form() | {error, ErrorInfo} | {eof, Line}
Line = erl_anno:line()
ErrorInfo = erl_scan:error_info() | erl_parse:error_info()
Extra = [{encoding, source_encoding() | none}]
OpenError = file:posix() | badarg | system_limit
Preprocesses and parses an Erlang source file. Note that the tuple {eof, Line} returned at end-of-
file is included as a "form".
If extra is given in Options, the return value will be {ok, [Form], Extra} instead of {ok,
[Form]}.
parse_file(FileName, IncludePath, PredefMacros) ->
{ok, [Form]} | {error, OpenError}
Types:
FileName = file:name()
IncludePath = [DirectoryName :: file:name()]
Form =
erl_parse:abstract_form() | {error, ErrorInfo} | {eof, Line}
PredefMacros = macros()
Line = erl_anno:line()
ErrorInfo = erl_scan:error_info() | erl_parse:error_info()
OpenError = file:posix() | badarg | system_limit
Equivalent to epp:parse_file(FileName, [{includes, IncludePath}, {macros, PredefMacros}]).
default_encoding() -> source_encoding()
Returns the default encoding of Erlang source files.
encoding_to_string(Encoding) -> string()
Types:
Encoding = source_encoding()
Returns a string representation of an encoding. The string is recognized by read_encoding/1,2,
read_encoding_from_binary/1,2, and set_encoding/1,2 as a valid encoding.
read_encoding(FileName) -> source_encoding() | none
read_encoding(FileName, Options) -> source_encoding() | none
Types:
FileName = file:name()
Options = [Option]
Option = {in_comment_only, boolean()}
Read the encoding from a file. Returns the read encoding, or none if no valid encoding was found.
The option in_comment_only is true by default, which is correct for Erlang source files. If set to
false the encoding string does not necessarily have to occur in a comment.
read_encoding_from_binary(Binary) -> source_encoding() | none
read_encoding_from_binary(Binary, Options) ->
source_encoding() | none
Types:
Binary = binary()
Options = [Option]
Option = {in_comment_only, boolean()}
Read the encoding from a binary. Returns the read encoding, or none if no valid encoding was
found.
The option in_comment_only is true by default, which is correct for Erlang source files. If set to
false the encoding string does not necessarily have to occur in a comment.
set_encoding(File) -> source_encoding() | none
Types:
File = io:device()
Reads the encoding from an IO device and sets the encoding of the device accordingly. The position
of the IO device referenced by File is not affected. If no valid encoding can be read from the IO
device the encoding of the IO device is set to the default encoding.
Returns the read encoding, or none if no valid encoding was found.
set_encoding(File, Default) -> source_encoding() | none
Types:
Default = source_encoding()
File = io:device()
Reads the encoding from an IO device and sets the encoding of the device accordingly. The position
of the IO device referenced by File is not affected. If no valid encoding can be read from the IO
device the encoding of the IO device is set to the encoding given by Default.
Returns the read encoding, or none if no valid encoding was found.
format_error(ErrorDescriptor) -> io_lib:chars()
Types:
ErrorDescriptor = term()
Takes an ErrorDescriptor and returns a string which describes the error or warning. This function
is usually called implicitly when processing an ErrorInfo structure (see below).
ERROR INFORMATION
The ErrorInfo mentioned above is the standard ErrorInfo structure which is returned from all IO modules.
It has the following format:
{ErrorLine, Module, ErrorDescriptor}
A string which describes the error is obtained with the following call:
Module:format_error(ErrorDescriptor)
SEE ALSO
erl_parse(3erl)