.TH erl_id_trans 3erl "stdlib 4.2" "Ericsson AB" "Erlang Module Definition"
.SH NAME
erl_id_trans \- An identity parse transform.
.SH DESCRIPTION
.LP
This module performs an identity parse transformation of Erlang code\&. It is included as an example for users who wants to write their own parse transformers\&. If option \fI{parse_transform,Module}\fR\& is passed to the compiler, a user-written function \fIparse_transform/2\fR\& is called by the compiler before the code is checked for errors\&.
.LP
Before the function \fIparse_transform\fR\& is called, the Erlang Compiler checks if the parse transformation can handle abstract code with column numbers: If the function \fIparse_transform_info/0\fR\& is implemented and returns a map where the key \fIerror_location\fR\& is associated with the value \fIline\fR\&, the compiler removes column numbers from the abstract code before calling the parse transform\&. Otherwise, the compiler passes the abstract code on without modification\&.
.SH EXPORTS
.LP
.B
parse_transform(Forms, Options) -> Forms
.br
.RS
.LP
Types:

.RS 3
Forms = [erl_parse:abstract_form() | erl_parse:form_info()]
.br
Options = [compile:option()]
.br
.RE
.RE
.RS
.LP
Performs an identity transformation on Erlang forms, as an example\&.
.RE

.LP
.B
parse_transform_info() -> Info
.br
.RS
.LP
Types:

.RS 3
Info = #{\&'error_location\&' => \&'column\&' | \&'line\&'}
.br
.RE
.RE
.RS
.LP
Returns information about the parse transform itself\&.
.RE

.SH "PARSE TRANSFORMATIONS"

.LP
Parse transformations are used if a programmer wants to use Erlang syntax, but with different semantics\&. The original Erlang code is then transformed into other Erlang code\&.
.LP

.RS -4
.B
Note:
.RE
Programmers are strongly advised not to engage in parse transformations\&. No support is offered for problems encountered\&.

.SH "SEE ALSO"

.LP
\fIerl_parse(3erl)\fR\&, \fIcompile(3erl)\fR\&