.TH epp 3erl "stdlib 1.18.1" "Ericsson AB" "Erlang Module Definition"
.SH NAME
epp \- An Erlang Code Preprocessor
.SH DESCRIPTION
.LP
The Erlang code preprocessor includes functions which are used by \fIcompile\fR\& to preprocess macros and include files before the actual parsing takes place\&.
.SH DATA TYPES
.nf

\fBmacros()\fR\& = [{atom(), term()}]
.br
.fi
.nf

\fBepp_handle()\fR\& = pid()
.br
.fi
.RS
.LP
Handle to the epp server\&.
.RE

.SH EXPORTS
.LP
.nf

.B
open(FileName, IncludePath) ->
.B
        {ok, Epp} | {error, ErrorDescriptor}
.br
.fi
.br
.nf

.B
open(FileName, IncludePath, PredefMacros) ->
.B
        {ok, Epp} | {error, ErrorDescriptor}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
FileName = \fBfile:name()\fR\&
.br
IncludePath = [DirectoryName :: \fBfile:name()\fR\&]
.br
PredefMacros = \fBmacros()\fR\&
.br
Epp = \fBepp_handle()\fR\&
.br
ErrorDescriptor = term()
.br
.RE
.RE
.RS
.LP
Opens a file for preprocessing\&.
.RE

.LP
.nf

.B
close(Epp) -> ok
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Epp = \fBepp_handle()\fR\&
.br
.RE
.RE
.RS
.LP
Closes the preprocessing of a file\&.
.RE

.LP
.nf

.B
parse_erl_form(Epp) ->
.B
                  {ok, AbsForm} | {eof, Line} | {error, ErrorInfo}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Epp = \fBepp_handle()\fR\&
.br
AbsForm = \fBerl_parse:abstract_form()\fR\&
.br
Line = \fBerl_scan:line()\fR\&
.br
ErrorInfo = \fBerl_scan:error_info()\fR\& | \fBerl_parse:error_info()\fR\&
.br
.RE
.RE
.RS
.LP
Returns the next Erlang form from the opened Erlang source file\&. The tuple \fI{eof, Line}\fR\& is returned at end-of-file\&. The first form corresponds to an implicit attribute \fI-file(File,1)\&.\fR\&, where \fIFile\fR\& is the name of the file\&.
.RE

.LP
.nf

.B
parse_file(FileName, IncludePath, PredefMacros) ->
.B
              {ok, [Form]} | {error, OpenError}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
FileName = \fBfile:name()\fR\&
.br
IncludePath = [DirectoryName :: \fBfile:name()\fR\&]
.br
Form = \fBerl_parse:abstract_form()\fR\&
.br
     | {error, ErrorInfo}
.br
     | {eof, Line}
.br
PredefMacros = \fBmacros()\fR\&
.br
Line = \fBerl_scan:line()\fR\&
.br
ErrorInfo = \fBerl_scan:error_info()\fR\& | \fBerl_parse:error_info()\fR\&
.br
OpenError = \fBfile:posix()\fR\& | badarg | system_limit
.br
.RE
.RE
.RS
.LP
Preprocesses and parses an Erlang source file\&. Note that the tuple \fI{eof, Line}\fR\& returned at end-of-file is included as a "form"\&.
.RE

.LP
.nf

.B
format_error(ErrorDescriptor) -> io_lib:chars()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
ErrorDescriptor = term()
.br
.RE
.RE
.RS
.LP
Takes an \fIErrorDescriptor\fR\& and returns a string which describes the error or warning\&. This function is usually called implicitly when processing an \fIErrorInfo\fR\& structure (see below)\&.
.RE

.SH "ERROR INFORMATION"

.LP
The \fIErrorInfo\fR\& mentioned above is the standard \fIErrorInfo\fR\& structure which is returned from all IO modules\&. It has the following format:
.LP
.nf

    {ErrorLine, Module, ErrorDescriptor}    
.fi
.LP
A string which describes the error is obtained with the following call:
.LP
.nf

    Module:format_error(ErrorDescriptor)    
.fi
.SH "SEE ALSO"

.LP
\fBerl_parse(3erl)\fR\&