epp(3erl)

NAME

   epp - An Erlang code preprocessor.

DESCRIPTION

   The  Erlang  code  preprocessor includes functions that are used by the
   compile module to  preprocess  macros  and  include  files  before  the
   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  matching  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

   close(Epp) -> ok

          Types:

             Epp = epp_handle()

          Closes the preprocessing of a file.

   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.

   format_error(ErrorDescriptor) -> io_lib:chars()

          Types:

             ErrorDescriptor = term()

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

   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 specified in Options, the return value is {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}]).

   parse_erl_form(Epp) ->
                     {ok, AbsForm} |
                     {error, ErrorInfo} |
                     {warning, WarningInfo} |
                     {eof, Line}

          Types:

             Epp = epp_handle()
             AbsForm = erl_parse:abstract_form()
             Line = erl_anno:line()
             ErrorInfo = erl_scan:error_info() | erl_parse:error_info()
             WarningInfo = warning_info()
             warning_info() = {erl_anno:location(), module(), term()}

          Returns the next Erlang form from the opened Erlang source file.
          Tuple {eof, Line} is returned at the end of the file. The  first
          form  corresponds to an implicit attribute -file(File,1)., where
          File is the file name.

   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. Notice that tuple
          {eof,  Line}  returned  at  the end of the file is included as a
          "form".

          If extra is specified in  Options,  the  return  value  is  {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}]).

   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 is found.

          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 is found.

          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 I/O device and sets the encoding of
          the  device  accordingly.  The  position  of  the   I/O   device
          referenced  by File is not affected. If no valid encoding can be
          read from the I/O device, the encoding of the I/O device is  set
          to the default encoding.

          Returns  the  read  encoding,  or  none  if no valid encoding is
          found.

   set_encoding(File, Default) -> source_encoding() | none

          Types:

             Default = source_encoding()
             File = io:device()

          Reads the encoding from an I/O device and sets the  encoding  of
          the   device   accordingly.  The  position  of  the  I/O  device
          referenced by File is not affected. If no valid encoding can  be
          read  from the I/O device, the encoding of the I/O device is set
          to the encoding specified by Default.

          Returns the read encoding, or  none  if  no  valid  encoding  is
          found.

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_parse(3erl)

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